Honestly, I have a terrible time at finishing games and it's definitely something I need to work on. I struggle with finishing games for a similar reason as you - I have quite a few games at this point that I find myself bouncing around from game to game
a lot. When I was only getting one or two games a year they were really special and I was sure to finish them (or get as close as I could to finishing them) because I didn't really have a lot of options. Once I was making my own money though and had the ability to buy my own games I would always jump on them as soon as I could. Which I don't necessarily mind simply because certain games can become hard to find later on and I'm happy to have them in my collection! But I'd always open them up right away, play a little bit, and then I'd either get a new game or I'd switch to a different one.
I want to try and revisit some old games and work on finishing them because I do have a lot of games that I know are fun! I just... get a little discouraged once things get a bit too tough. I'm not very good at games
so a lot of my issues stem from me running away from a challenge and then... never really coming back. It's especially bad on my 3DS because now that I have my Switch there's a part of my brain that was like, "those are old games!!! They don't need to be finished play something new!!" which is super silly, lmao.
I do find that for myself personally smaller games are definitely better. I get drawn in by the premise of these big open world, choose your own adventure, style of games but they are
so overwhelming a lot of the time that I never beat them or even get that far into them! Whenever I see game reviews complain that a game is ~too short~ that usually peaks my interest, as long as it's not like 4 hours for a $90 game because that's a little disappointing.