I play mostly casual, tho I do try to catch and use Pokémon with good natures, since me and my friends will battle sometimes. Past that I just like to do favorites! I often like to breed Pokémon with correct natures to use if I decide to do a new run on a game. I did raise a competitive Pokémon once. A high I.V. Espeon that I EV trained. I was proud of it, but I disliked the process so much that I never wanted to do it again lol.
I am a casual at the games. I personally just like going through a game and having fun with a team I've caught over my journey. I usually pick out Pokémon I like before I start so I can easily balance my team, but other than that, I don't do anything competitive at all. Now with TCG, I actually have a seriously good competitive eye to the point where I can just look at a card's moves/effects and determine if its viable or not. I haven't actually played competitively in TCG, but I do want to someday.
Casual to official Pokémon games. But for fangames..... Super competitive. I am currently Pokémon Reborn. Which is basically an extreme version of Pokémon. I have to be the god of competitive players to win without retries.
I played competitive from 2004 to 2016, and still breed competitive Pokémon and occasionally do a match or two. I fell out of competitive Pokémon when Sun and Moon were released, for a variety of reasons. I love competitive Pokémon, but I also find value in Pokémon that aren't very good in competitive, too. I don't think liking one has anything to do with the other. It's entirely possible to know that Shuckle isn't gonna win you many high level games and still love it because it's Shuckle.
My interest in competitive has been few and far between. I'm not against it by any means, but it has never been high in my priorities while playing Pokémon. I appreciate a lot of what the competitive scene does, but I have the most fun when doing a playthrough full of Pokémon I haven't tried before.