It may be a mix of both, but generally the developers for each game decide how the online works. Splatoon's online is not very good for grouping with friends (it's....
possible but unless you're both good and can be in a squad then it's not worth it), but I'd say it's otherwise much better than Smash Ultimate's online.
And, Super Mario Maker 2's online is looking better than ever. I mean--online Mario platformer multiplayer? That's a first, as far as I know. We'll have to see how it is in action though.
Other games that are on the Switch can do online multiplayer much better, such as Rocket League or Paladins, especially when it comes to grouping with friends and playing the type of matches you want. So again....it's really Sakurai's fault in this case.
EDIT:
I don't let GSP bother me personally, but like
OnyanRings
said, it's unsatisfying seeing it decrease just because you're playing the game. Take the aforementioned Rocket League and Paladins for example: regardless of whether you win or lose a match, you're always seeing numbers
increase--usually in the form of level experience or whatnot, which will eventually grant bonuses of their own. So you never feel like you were wasting your time. It may seem like a little thing, but I think it makes a big difference now that I know what it's like when something like that is not only absent, but actively working in an opposite fashion.
ANOTHER EDIT: I guess there are coins but....I've got plenty so that doesn't really do much for me and I usually don't even notice that I earn them.