To say that traits and behaviors are extraneous to the types and to dismiss them as "superficial" isn't really correct. Enneagram tries, in the first place, to outline stable differences between individuals, to highlight how different two people can be and how differently they can experience the world, and to challenge ourselves to notice when our automatic habits don't really help and to develop ourselves from that habit of observation. When Enneagram was created in the 1950s-1970s, the heritability of personality wasn't much of a topic for research, and the general idea was more on the side of nearly everything being learned through life experience. As people clearly are very different from each other, there has to be something that made them so, right? People aren't different for no reason.
To get at where the Enneagram goes wrong, one huge thing is what it considers to be the root of personality structure and differences between people. Most takes posit that people have some kind of fundamental experience that leads to the formation of a motivation that then over time results in the construction of an ego structure, and these motivations relate to over- or underexpressing three key emotions. But is that really how it goes?
Just on the face of it, if you really think every human's personality is fundamentally driven by anger, shame or fear, I've a bridge to sell you. Good condition, inland, nowhere near a body of water.
The motivations themselves suffer from a similar problem: They're just too specific and narrow to really characterize human personality as a whole. You can find some of them in most people, to be sure, but that doesn't mean they're the fundamental building block of those people's character. To claim so would require pretty extraordinary evidence. Furthermore, those motivations have to come from somewhere, and that's where things get interesting.
As far as behaviors go, the detractors are right when they say just focusing on behavior doesn't quite work, but "looking at the motivations", yeah. We still have that bridge in stock. The problem with looking at behaviors is the same as with the motivations: Where do they come from, since eg. lashing out at someone rudely can be born of many different things.
Fundamentally, humans - any creatures - need reasons, causes for acting the way they do. Any creature only takes action because the rewards seem to outweigh the costs, and the systems that gauge how profitable or enjoyable rewarding signals are differ naturally between people - give someone with a high reward sensitivity the same set of inputs as someone low in reward sensitivity, and one will see a world abundant in opportunity to be seized and joy from things acquired, while for the other the rewards seem lower, and thus the costs seem higher in comparison, and he will see more of the world as a drain or a drag, more trouble than it's worth. There will still be things that filled their heart with joy and they'd totally end up doing those things, but their sphere of concerns would inevitably be smaller than that of the reward sensitive person, all else being equal. This is just a simple consequence of both perceiving similar costs but one sees things as more rewarding than the other - what those specific things are is of course very personal, but a highly reward sensitive person's sphere of interests will be wider, on average and they will exhibit more positive emotions since wanting things and liking things is what drives us to pursue rewards in the first place.
The above is the true definition of Extraversion, and in contrast to the Jung-born popular idea of a scale of "turned outwards and shallow" vs. "turned inwards and deep", it's a trait that goes from "a lot of outward-engagement" to "little outward-engagement" and doesn't really have a negative pole or an opposite. Enthusiastic engagement vs. lack of interest rather than extraverted and introverted, per se. The classic, ruminative depth some people possess is due to different personality traits, different systems.
From the get go we see that the motivation and "superficial" behavior are linked - there's no way they couldn't be, since the behavior needs a cause to happen to begin with, an inner experience that motivates the action. They're inextricably linked. The big thing is that you need to be wary of what things you look at - you can end up in certain places by many different roads. If you try to focus on words like industrious, headstrong and opinionated when trying to discern whether someone is a One or an Eight, you'll never make heads or tails of it, which is what the warning is for. But not all superficial things are like that - some are very, very good information sources since they reflect different levels of the underlying traits.
To illustrate further, take the example of someone chewing another person out. They must be really angry, right? Well, they might be. Someone with a high degree of dispositional empathy might need to get very, very angry until they get pushed over the edge to lash out at someone. Someone else with a really low degree of dispositional empathy would simply need to be a bit displeased and they might say hideous things.
To make things even more complicated, just as people differ in their reward sensitivity (and thus positive emotionality, eg. extraverts provenly like pictures of puppies more and stay happy for longer after seeing one), people differ in their degree of negative emotionality - put the same signal into two different people and one can get really distressed while the other reacts with a shrug. So the same signal could get a similar level of inconsiderateness out of a disagreeable, unempathetic person who's emotionally stable and from a person who's agreeable and empathetic but sensitive to things that provoke negative emotions. One gets irritated and protests in a very blunt, callous manner, while the other's overcome with emotion and lashes out. Same words, same antagonism, very different root causes.
It's easy to see how these kinds of dispositions could commonly lead to different kinds of outlooks on life - a person who really viscerally feels others' pain and someone more tough-minded are likely going to adopt different life philosophies, and so on, and they're also likely to act differently overall. But these philosophies are merely a consequence of the fundamental building block of temperament, and a lot of the individual variety in that is due to how our biological systems are wired, without any kind of clear cause. Just the opposite: The way our biological systems are wired colors our experience from the day we're born. We interact with the world according to our nature, and as the world responds to our actions, we absorb the feedback through the lens of our nature. We're certainly not slaves to it, but it colors, well, everything.
This is where the Enneagram writers make their biggest mistakes - they fabricate coping strategy -style reasons for behaviors since people's differences need a cause, and that results in some pretty bad misinterpretations. In a sample of 241 pre-typed people who were given a non-Enneagram personality test, for example, Eights scored the lowest on negative emotionality. Anger-driven? Nope, not by a long shot. Uncaring, callous? Sure, they tied with Fives for the style with the lowest degree of dispositional empathy. But the authors merely write of anger, when the feeling of anger, proper, means intense emotional investment and reaction to something, and Eights are the exact opposite. They just don't care about the other's feelings as much as most people so feel more free to express their displeasure. An Eight chewing you out feels bad - being displeased is still typically provoked by a negative signal - but the Eight's inner state's going to be just miffed. They're low-care, naturally assertive people so they'll talk things out kinda roughly before shit gets out of hand. Now, if it's a 9w1 chewing you out? A person high in dispositional empathy, not naturally assertive, and to boot also a bit less sensitive to negative emotional signals than average? Just imagine how bad a person like that has to feel to really lash out at someone bigtime.
So, some profiles are wrong. Some of the profiles are not mistaken, and actually often pretty good. Take the Nines mentioned above, for example. Bottle up their anger? Sure. High degree of dispositional empathy, very low extraversion (and so low Assertiveness), lower than average negative emotionality (so their problems don't seem so serious), and bam. Others' issues feel more important to the Nine than their own, and they end up swallowing their misgivings, which eventually leads to the outbursts written in the books.
Low reward drive and high empathy also easily explain why they find it easy to move for others but not so much themselves - their muted reward drive just doesn't see too many profitable things out there, and they are in any case unused to asserting themselves the way extraverts are, and the list goes on and on.