I just... don't agree, sorry. There definitely is a lot of gatekeeping in the gaming/"nerd culture" world that needs better addressing, but I do not think games being designed with a target audience in mind is gatekeeping. I do not expect Nintendo to ever add real difficulty options to their games, and that's fine; I'm not the target audience. I can still get some enjoyment out of the product, but it's not as fun for me as it is for younger people. There is nothing inherently wrong with that. Would I like them to cater to me? Yeah, sure, who wouldn't? This thread is full of people making that argument. But I'm not being "gate-kept" or personally attacked just because the game wasn't made in way that's easier for me to enjoy.
I DO think there should be a much bigger industry-wide focus on making things more accessible for disabled people - Microsoft has already started going down this road with their special controller - but that's out of the scope of this discussion.