Se is sense perception that simply perceives the object for what it actually is. Nothing deeper than that.
Si is sense perception that is subjective and removed from the actual object actually is. Only suggested by it.
What most people here is talking about, is largely the certain forms of mentalities that might be subscribed towards Si and Se (particularly if it's in the dom form).
Maybe it's just me, but I don't really think I'm all that past focused as most Si descriptions are though, so I might not be an authority on this subject though *shrug*.
In fairness ive never related to any description of any ISJ type, ever. Also people forget that Si, being an introverted function, will be intensely different from person to person, the outline of what the function is might stay the same but the way it presents itself is very varied.
The mentality of enforcing the worldview on the environment around it or rather keeping it's influence at a distance, classic introversion which appears to be exacerbated by Si in particular, is also something I can say ive never noticed in myself, nor has anyone else. However the idea is that the impressions are so subtle as to be invisible to an Si dominant, so through that the impressions being forced on others can be small and insignificant, but over time build up into an entire way of doing things that permeates an environment.
I imagine if this were true, a good example would be the boss of a workplace and his or her work ethic would be communicated as the rule in the business. So the more control the more influence on the environment. As Jung mentioned the type becomes a menace to their environment.
But then again this goes for several other types as well. As for past oriented, i'm with you on that, oh there is sometimes nostalgia, but it's never a powerful longing.
I generally experience a preference for what is to come than what was. I only dwell on past events when i'm stressed. Then I might play a situation over and over and wonder on how I could have some something different, or how it might have unfolded differently.
Also problem solving is an interesting one. Most would assume that Si would induce someone to do something the same way every time and review past information so as to come up with a solution. But I think most people would review past information, Ne for example needs Si in order to jump to new ideas through past data collection.
That always has a place and for myself I tend to improvise and do something a lot differently than others would normally do it when i'm solving an issue.
I tend to see Si as actually being more complex and harder to understand than Ni.
Ni is, to me, a way of hollowing something out so as to find out what lies behind something, it's all about depth, going further reading into something more and more, whirring away behind the eyes, until it comes up with a new concept that can be applicable, just not at this moment in time, it's something that will be conceivable using the information around us, it's just most don't perceive that well. For example if an Ni dom were to examine a cup they might instantly be struck by a notion of changes that might come about in terms of water purification. Of course this is a pragmatic, literalist interpretation, in truth there is also a lot of intangibility to Ni as well. Usually an Ni perception is hard to put into words because of this.
They suppress as much as possible the literal Se sensory interpretation of the physical object in front of them and instead that fades into obscurity, what remains is the concepts excited by that stimulus which then leaps and bounds to arrive at a point far beyond the reach of most and a point others usually find is barely connected, if connected at all. But to an Ni dom it is and obviously so, if only people would just LOOK.
Si on the other hand I actually struggle with. The subjective impression of the objective consideration, I mean where to begin. It isn't a surprise that Jung wrote of archetypes a lot, especially when concerning Si. For Si the catalogue of impressions is intensely personal and...well...bizarre.
Physical objects take on lives of their own, they have personality and the surface of them is the shadow, what is real is the bit behind them, the subjective impression. "This is not just any teddy bear, it is my teddy bear it is the archetype of all teddy bear's to be and to come, no teddy shall deviate from my teddy lest it be found wanting".
Of course that's an extreme example and I believe a balanced and healthy Si dominant is far from that level of....tyrantism towards their environment. But still, I find the idea hard to grasp because of the sheer....symbolic randomness of it.
The Si dom doesn't even know what will catch their attention. They could eat a thousand variations on cauliflower cheese for example and never come to a conclusion on what they like best. But then when eating tomato soup once, they suddenly find that this is THE tomato soup and they try to replicate that, try to bring back some of that magic flavour.
In a metaphorical sense you could say that is how it works; flavour. The flavour of reality; what does it taste like? What does it smell like? Ignore mere sensory information, this is an explosion of human cognition at work applying meaning to our impressions. But these are questions asked with the fixation of 'to me'.
So how does the world taste, to me?
And I wonder how it tastes to you?