Personally even though i think dsp is an undiagnosed Autist. It is also plausible that his whole behavior and attitude can be attributed to how his parents raised him and his hermit lifestyle aka not leaving or interacting with real life people outside annd only being in his social bubble with "Yes people" aka the chat. All that and the fact that he barely goes out and does Matuur adult things can dull people's social skills to the point that they start to mispronounce words. I believe if he went out more, socialize with people more and overall just be outside more, that could help him readjust himself and who knows maybe he would stop being such an asshole.
We all know he wont go outside like that because hes a lazy fuck.
While there are a lot of similarities between young Phil and present day Phil, it is interesting to go back every now and then and see the differences. I mean, just the fact that young Phil was willing to step outside his gout fort and film vlogs is a huge difference. A few days ago there was the hypothetical "what if DSP went on vacation" question, with most people saying it wasn't even worth entertaining because the very idea of present Phil leaving his home and going on vacation seemed impossible, but there was a point where Phil was willing to leave the state and actually interact with people. Sure, he still spent the majority of the time in the hotel, but still, it's practically night and day compared to who Phil is now. Arguably the biggest difference is Phil actually had friends during this period in his life.
Phil was always lazy, and his commentary was shit, but it was at least vaguely present. If I had to choose between watching older Phil content versus watching newer Phil content, and anything with a remotely sharp edge was stripped from the room so I had no choice but to actually watch, I'd pick younger Phil. You can definitely track the decline with Phil, and it largely boils down to two things, his drinking and his lack of friends. Drinking obviously killed his brains, and lack of friends is what turned him into a hermit. I'm not saying Phil wouldn't still become a gacha addict if he had friends, but I think a large part of why he turned to Champions is he genuinely has little else in his life to fill his time.
All that being said, it's possible on top of all those things, Phil is autistic, but even if that's the case, I think you can still attribute his overall decline to other factors. It's not like all autists are as socially inept as Phil or as terrible at games or the like. Hell, for better or worse (definitely worse) a straight up retard like Derich has more of a social life than Phil. And even his dents sometimes manage to go on vacations or have friends, and at least possess enough critical thinking to get through basic video game puzzles. So at most, Phil's autism contributes to his general disposition, but it is by no means the sole cause.