The slut one does get used, especially for Se-doms, actually. Those that haven't developed their aux properly yet and are high on their dom tend to have this tendency. The problem is that it's also an escape mechanism for those with low-self esteem, so it gets labelled as problematic (like all dom functions on a rampage, basically). Meanwhile, because Fi does the whole 'jump passed pleasantries to get to the good, intimate stuff', it often gets the rep of being either a tease for establishing an intimate connection from the get go and then backing out of those 'promises' that that brings with it, or a slut when they (seem) combine that Fi intimate connection with that Se urge to experience things. Again, especially in ExFPs, because the Fi-aux is used like a parent function should - to 'love' and show affection to others. Meanwhile, ISFPs will do so with Se, which again can lead to the slut-stereotype, and INFPs will use silly Ne banter jokes to connect and love others.
And of course, calling someone a slut is the *best* way to discredit a woman socially, so it's a favourite tool for those that feel others aren't playing by social rules (such as Fi-users that tend to care less for that shit) and are behaving therefore inappropriately, and should therefore be penalised socially
That said, our way can occasionally and often unintentionally create false expectations with others, due to the intensity of connection we can generate by being, well..pretty damn forward with private information, getting others to talk to us, and in a way often unconsciously 'mining them for intimate data' out of sheer curiosity. That stuff tends to be reserved for a mate, for most types, so it can create an emotional one-night stand effect, leaving the other party feeling cheated out of something they were looking to invest in long-term.
As for the 'dumb' stereotype, it's due to the fact that we use Fi instead of Ti. Ti is our weak spot, and it's often equated with logic, critical thinking and just about anything else that is valued in society as 'intelligence'. Meanwhile, Fi-logic and wisdom is a lot like art. It's subjective, one has to develop an eye for it to really appreciate its 'usefulness' and impact, and its wisdom cannot be quantified, tested or peer-reviewed. And that makes it very hard to explain it, or teach it, or even appreciate it. There just isn't a straight forward way for that as it is individual to every person.
So there are plenty of people who don't get the value of Fi, some of who are very prone to discrediting anything that smells woo-woo to them and cannot be held up to their own critical yardstick while being absolutely certain that anything they cannot understand must be bullshit and yeah...the 'dumb' stereotype is born (the same is true from our side, with labels like 'cruel' and 'uncultured' being used). Again, it's very much understandable, because when you cannot verify something yourself (as you lack that skill set/preference to develop it) and it doesn't in *any* way make sense to the yardstick you've mastered, value and understand, it makes sense not to trust it in the least
From what I can tell, we're all equally stupid - just in different areas. It is certainly true that when it comes to Ti, we often fail miserably, and so, there is certainly
some truth to the stereotype, as is often the case with stereotypes. And because Ti is often prized in society, those who prefer it make no qualms about loudly proclaiming their preference the golden standard, the 'objective' label of stupid and dumb is stamped on those that cannot keep up with that standard. Which..ironically, fails the Fi-standard of balancing your own preferences and values with universal values and truth
Meanwhile,I can no longer count the amount of people I've met who have been confounded by the fact that somehow our kind can defy rules they considered unbreakable, or circumvent the only logical path they see to get to a goal and cannot for the life of them backtrack how we got there anyway, and not just that,
before them. Even when you explain to them how those people get there,
a few of them still look at you like you must be nuts for denying (and defying

) the laws of gravity somehow. That, or they accuse them of cheating and evil manipulative tricks
I swear they'd scream 'WITCHHHH!!!' at you, if they weren't so busy convincing themselves that witchcraft is a silly notion that is too ridiculous for words, only to be indulged in by wanna-be Harry Potters
I call it the Pinkie Pie Phenomenon:
With all this said, the amount of crude stereotyping like this (with our type as well as with others) has seriously declined on this forum over the years, so it's nowhere near as prevalent as it once was, which is definitely progress