The weakest skills are the ones that should be trained more. As obvious as that might seem a lot of people choose ignore that. For example you're playing a piece from the start and you get to that part where you know you'll mess up, so you play it badly, like you use to, sort of get it over with. Since that part is hard you dislike playing it (how could you like it if it sounds like crap when you play it?), but you enjoy playing the rest, easier parts of the piece, and you play those parts more because of that same reason. So you over-practice the easier parts and you don't practice enough the hard ones.
Same with pieces, maybe you don't like pieces that leap around because you're just not familiar with them, if they were as easy to you as the sonatinas you play I think you'd like them the same, or even more. With that in mind, you probably like playing pieces that are simple, with scales and arpeggios because those are the skills you've studied the most with Czerny and Hanon exercises. In my opinion, that's not right, because exercises could be determining your repertoire, when it should be the other way around.