There are two songs that can emotionally wreck me and both are associated with people I only went on a few dates with 
I don’t know shit, but I think this means I’m not over those people. Not even my ex did this to me.
If this makes sense, the thought of willingly subjecting myself to this feeling again seems awful but the crying kinda helps. Fuck
If my experience can help someone else it will feel less like needless suffering lol
What you call "fundamental incompatibility" is something everyone experiences. Even the "normal" people (they don't exist btw. This is part of the reason I prefer the terms neurotypical and neurodivergent because "typical" and "divergent" can describe a range of phenotypes rather than some binary system that only serves extremes). For a stark example, someone who is religious is less likely to want to be with a person that's not religious. That doesn't mean that the secular person in this example should torture themselves with "why couldn't I just believe in God so I could be with this person?"
That vulnerability cliff hurts a lot more to those people with trauma or atypical brains (kind of the same thing but I'm not going into those weeds). The really difficult part is telling that part of your brain it's okay to feel those things. Personally I avoid every emotion I could possibly exhibit ever to avoid attention, which I associate with humiliation even when the attention is good. The deprogramming starts with observing your reactions and learning to unburden your system from these protective jobs. Strongly encourage you to look into IFS because it probably saved my life
Focusing on your last comment:
You're probably familiar with the term "masking." Whether it's something systemic and unstable like the pandemic, personal relationships failing, or otherwise, eventually your system hits a critical point. Your system sort of exhausts itself from the act it's playing, that mask falls off and the system freaks out because now everyone can see it's different. Saying that you were a "semi-normal" person tells me you still struggle seeing yourself as defective or lesser because you feel things, or you can't handle stresses you could before. I think after that demasking happens, either the first time ever or as an adult, it's hard to accept you can't go back to pretending your brain operates within the typical range
At the end of the day I'm talking through a lot of my process and experiences, and I don't expect that all of this applies to you. However I do understand what it feels like to have that supreme lack of confidence in who you are because of a perceived regression. So I will tell you nothing is ever perfect but it does improve over time when you do the work
Yup, this almost describes an exact situation I was in with someone I’m still having trouble getting over :/ I’m not exactly sure why we were not compatible, but I think it had a lot to do with my mannerisms and how I interacted with other people (which is unfortunately a crucial factor I never thought about). I just look at them and see them as more normal (first thing that comes to my mind) even though I know that’s a bit silly to say because how exactly do you gauge normalcy?
I guess what I’m struggling to comprehend is that if everyone experiences this, why does it seem to feel so heightened/different?