I feel that.
M
MooMew64
too
What I have been doing right now is just going through every single member of the cast and checking performance with each character, whether it's against CPUs or human players. If you find a character that feels "natural" and do well with, then playing them more and seeing if you still like them. If you end up performing relatively well with them, or at least enjoying their character, then not only will you come to appreciate their inclusion in the game more, but you'll also 1.) have more fun with the game in general, and 2.) your performance will likely improve, even if it's a little bit, with a character that you love to play and just naturally meshes your playstyle.
With me, Ness is my boi. I love playing him and he fits my all-around playstyle: got some good combos, good mix-ups, and good KO moves. He's balanced and has a little bit of everything, and that fits me well because it doesn't restrict me to one format of play and it makes the game more fun for me. It's similar with me and discovering that I *really* enjoy playing Cloud in Ultimate half a week ago, despite HATING Cloud in Smash 4 and having a bad history with him before this month.
Mario's the opposite. I flippin' love his character; childhood favorite video game character and I used him all the time in Smash 4. But in Ultimate? TBH my Mario's not as good as what I would expect in Ultimate, because he's more rushdown/combo-heavy than ever before, and to be honest that just doesn't fit my playstyle. He has amazing combos in 4, but you can afford to play more "all-around" in 4 and control the pace of the game more frequently. But with Ultimate, if you're playing bait and punish Mario or any other kind of Mario other than rushdown/combo-heavy, you're doing it wrong. It's why he's been relegated to being a counterpick character at most; normally a "friendlies only" character.
Just pick who you have natural chemistry with, and you'll appreciate the game more in many ways.