I played Kirby in smash 4 for some ungodly reason, instantly dropped him in ultimate when I saw his forward throw gets stuck on platforms now, and the fact he got no significant buffs from the last game.
King K. Rool ended up being my first ultimate main, followed by Ridley. My initial impression of Ridley was that he felt "weird" and I didn't like playing as him, so at first I just... didn't. But one day, I'm looking at Ultimate's roster and thinking how amazing it is that we finally have King K. Rool and Ridley in the game. and then I thought how UN-amazing it was that after over a decade of me desperately wanting to play as this cool purple space dragon after first seeing him in Melee's opening movie, that I'm just... NOT playing as him! To make matters worse, it seemed like NOBODY online was playing him! This character that had so much vocal outcry and support over the years was just... sitting there, collecting dust on the character select screen. So I decided; "Screw it. I've wanted to play as this character ever since I was a kid, and that's EXACTLY what I am going to do! I don't care how bad he is! I don't care how weird he plays! I AM GOING TO PLAY AS RIDLEY IN SMASH."
So I popped him into training mode and figured out the basics. Most importantly I learned how many jumps he had (only 1 extra jump?!) and how his up b works (only 4 angles?!) Then I just played him in free for alls for a while. Now that I wasn't constantly running out of jumps or trying to do Fox angles while recovering, I quickly found myself having alot of fun with the character. As my confidence with Ridley grew, I eventually took him to team battles, and then 1v1s, where he quickly became a trusty secondary to King K. Rool. In fact, it wasn't long until Ridley surpassed K. Rool and became the primary main, with K. Rool eventually being dropped altogether.
Ridley remained as my solo main until Pyra was released as DLC. I hadn't played XB2 at the time (I still haven't played Metroid either lol) but I was a big fan of her design. The fact some people get so mad at fanservicey characters, and by extension her inclusion in smash, also fills me with a certain trollish delight

I was quite used to "unga bunga, me hit hard" characters by this point, so her moveset was a natural fit and she reached secondary status pretty much instantly. Mythra... exists. I'm very bad with fast characters so I generally don't use her outside of recovery.
Casually I enjoy playing a large variety of characters. Due to the way Ultimate's arenas work I usually just stick to playing Random so I don't have to give up my spot in line to change characters. I sometimes consider Random to be my third main XD