I think a trap a lot of artists at your general skill level fall into is falling short of your expectations for yourself on a piece. It’s kind of the paradox of being knowledgeable enough to understand what you need to work on in a piece, but not quite having the skill development to execute it to what you think you should be capable of. All artists hit that point, and it is very hard to get out of, and in some forms impossible since no one can be perfect at every type of art.
That notwithstanding, my advice for your situation is work faster. You say you don’t spend enough time on backgrounds, but maybe you’re just spending too much time everywhere else. Not every drawing needs to be fully rendered out and a showcase of all of your acquired skills. Rendering takes a lot of time, so maybe try stripping down your work process to be more focused on the broader strokes, and then if there’s one you really really like render it out fully. It’s better to spend a few hours and have a bunch of studies that are getting incrementally better, than spending that same time on one piece that you’re frustrated at and only got the growth in skill one of those quick studies would have netted you.
I understand your feeling of the piece not being a whole, or that the individual parts of it are disconnected in some way. I was in that place for a long time (and still am in a lot of ways). The best thing to solve that issue is work on compositions. Block out the general structure of your foreground, midground and background before you begin drawing. Follow the general composition format templates like the rule of thirds, golden spiral, strong diagonal etc (I’d give you links but I’m on Mobile sorry) and then build the drawing out from there so that everything has its general place built in. Also pay really close attention to the scale of the background items. For example: If there’s a character standing a few feet in front of a house and they’re the same height it creates a discrepancy, same when two background elements are out of scale with scale as well.
Another trick is to have elements in front of each other, even if a character is the focus, having a plant, or a wall or anything obscuring them a bit really puts them in the world of the drawing more (even more so if they’re interacting with the objects).
Don’t feel bad if you feel like your art isn’t good, you’re learning a skill, nobody comes out with all of the knowledge to draw perfection. The important thing is that you push through and keep drawing stuff you enjoy drawing. Keep recognizing where you can improve, and, most importantly, choosing to put the work in to improve.
