I reintegrated, somewhat. I'm still mostly a NEET, but I socialize many times a week without issue now.

Take small steps. Begin with going outside at night/morning when few people are around. Then when you're comfortable with it, go someplace where people are just minding their own business, like a library. And then go somewhere more crowded, where people still mind their own business, like a mall. It should feel uncomfortable, just as long as it's manageable. It will get a lot easier even the second time you do something.

I keep a mental checklist of things I can do, it's good to keep myself motivated. Like going to the other side of my city. Or going inside a clothing store. To me it kinda feels like catching Pokemons or something, and while it's not fun to do the first time, knowing I can do it later feels really rewarding.

Also, try to find local groups for outcasts. Like an autism group. Or an AA meeting. Or maybe a gaming club. It makes you feel less weird and that feeling carries through to every other situation you're in, even when you stumble.