I really don't care about the Physical / Special split, although once you learn it, it does make the game easier. So I guess I'd hate for it to go away now *cough* I never understood it till Gen 6.... and I've played since Red and Blue lol.
Like others, removing run would just kill my interest in playing. I am glad we started starting with them. Like others said, it would be nice if we didn't have to mash the b button all the time.
Fishing..... oh boy.... while I love fishing, Sun and Moon just COMPLETELY killed it for me. I haven't fished at all in Sword and Shield because I hate how it is now. Why in the world did they make it fishing spots instead of just free form fishing.
Infinite TMs - Again... this killed me in Sword and Shield and now Sinnoh Remakes... why are we reverting back to some of the dumbest things in the game series?
Masuda Method - While I care nothing about IVs/EVs since I don't battle at all, it would suck for MM to be removed, although I have wondered if it actually has. I still have yet to get a Shiny in Galar from an egg and I am using the same ditto I've always used. Anyway, since Gen 5, I have shiny hunted, but I feel like if it was removed, I wouldn't hunt for shiny pokemon anymore.
Shiny Pokemon - I don't know if I'd like shiny pokemon being removed. I would probably end up going back to how it was in Sinnoh games and never touching it after I finish the dex. I will say that I wish that the would make a new type of shiny pokemon or something. The ribbons or achievement in Sword and Shield were a good start, but I don't think 90% of player if know what they are. I still don't really know what they are, I do know it is a special capture if you catch a certain pokemon at a certain time/weather.
But with us going toward internet more, I wish they would make seasonal wild pokemon and allow us to catch like special Christmas/Halloween/Season Color shiny pokemon.