Nothing wrong with making funky sketches that are just kind of abstract expressions, you say you're not good at self expression, but these feel like really good examples of self expression. You don't need to be "good" at art to still enjoy doing it. In fact, I'd recommend against just trying to get good for the sake of it, you'll enjoy art a lot more as self expression, as just a fun hobby rather than trying to turn it into a career or something more serious. If you just draw for fun you will get better, though slowly.

I think you need to ask yourself what "better" actually means for you and what you're trying to accomplish by getting "better". All of these pieces look fine to me, not saying you shouldn't want to improve, but "better" is always relative. As someone who has done art professionally for years, it's never good enough, you'll always feel like your art is not quite right and there will always be something "better" out there. There'll always be mistakes and things that don't look good to you. The trick is to just make peace with that uncomfortable feeling and not let it hold you back.

All that said, if you do just want to improve on a technical level, getting good is unfortunately just practice. Specifically, practicing drawing from real life. There's a reason that first year art students learn to draw a lot of still life pictures and draw live models. You need to know the "rules" of what things look like in order to "break" those rules better. You can draw an abstract or cartoony human face much more easily if you know how a realistic face is put together. You need to learn how to break things down into parts so you can "reassemble" them in the way you want. Practice drawing things in your environment, or use a photo of a person as a reference. If you really want, most towns and cities do have art modelling sessions that you can go to and just sketch a random person (they usually cost money though).

This just takes time, the more you practice the better you get. And it isn't fun, it's specifically drawing things you don't really want to so you can get better at drawing the things you do want to. And it won't feel relevant while you're doing it either, it'll feel kind of like a waste of time sometimes, and it will look awful, especially at first, but that's ok, it's practice, it isn't about making it look good, it's about learning and getting better at the skill, understanding how things fit together and how you can put them together in the way you want.

To answer your specific questions at the end:

What should I spend my extremely limited practice time on?

Whatever you want! Draw for fun if you want, practice drawing things around you if you want instead, don't try to "min/max" your drawing time, it'll just suck the fun out of the hobby and you'll just resent drawing. Practice if you feel like it, draw for fun if you feel like it.

How can I incorporate the things I like about others' art into my own? Do I just straight up try to copy them?

Yes! Copy the shit out of them, contrary to what some artists will say, having eyes and using them to look at art isn't "stealing" it. All art is inspired by previous art, no one makes things up out of whole cloth. Just wear your references on your sleeve, don't copy or trace someone else's work and pretend you came up with it yourself, just be honest. Tracing someone else's work is a great way to learn how they did it.

Usually when I'm trying to learn someone else's style, I'll start by tracing a picture I like, learning how and why they drew things in that way, and learning how I can adjust the way I do things to make it look more like theirs, as well as learning which parts of their art that don't really work, the little mistakes and errors (and every artist makes them!). Then, I'll use a picture as a reference to make sure I understand how their style works, sometimes it takes a while, but I can eventually get a passable imitation of their style and can then incorporate it into my own work.

Some people I've asked irl have said it's just a matter of time. I haven't been creating long enough to be good yet. Is there any truth to this? Am I just impatient?

Two years and you're not a master of the craft yet! You're fine. I've been drawing art for over a decade, half of that professionally, and my stuff still looks like garbage. It's more about mindset than it is about "getting good." There's a really cool feeling you get from learning art where you'll be able to just...draw things you couldn't before, you'll know how to do something you previously had no idea how to do. It's the most satisfying part about learning a hobby in my opinion. And in turn, you will have times (sometimes years) where it feels like you're not improving at all, that's normal and nothing to be worried about (even if it does suck while you're going through those times).

Just keep drawing and you'll get better, the more time you spend actively trying to practice the faster you will improve, but the less fun you'll be having. Just go at your own pace and do what feels comfortable, which is another thing that unfortunately takes practice to learn how to do, you've just got to figure out what works for you.

I would not recommend becoming a professional artist as a job though, it really does suck the enthusiasm out of the hobby and the pay is terrible. I'm an artist because I couldn't really survive doing anything else, not because it's a "dream job" or anything. Like any job under capital, it is just draining and soul crushing. As a hobby it can be really rewarding though.