As a non-artist that grew in up in a home full of artists, the biggest piece of advice I can give is take a step back from it all. Maybe that's a day, or a week, doesn't matter. Getting aggravated chasing something isn't going to change anything, nor is criticizing everything you do. I'll reiterate, walk away and try something new, something different. If you're doing the same thing all the time, it gets old, and quick. It becomes a routine, and when it becomes a routine, some of the creativity that inspired the work in the first place may go with it. New, fresh eyes may give you that "AHA" moment you are looking for.
If you think your lighting is trash, then work on that for the time being. Go to a park, or art gallery, or something of the sort and study it. See how the real world is lit up and what types of shadows are created at what angles, or see how artists apply their lighting and light sources. You can also take that as a chance to broaden your horizon's some, immerse yourself into art or surroundings you wouldn't normally find yourself in (within safe means, of course.). From what I'm seeing on your progress thread, though, your lighting is hardly trash. Maybe a bit dim in spots with just quick glances, but not at all trash. Better than a lot of other devs out there, at the very least.
Don't be afraid to push your boundaries and experiment, either. This is more of fine artist approach, but sketch things - inspirations. If you can't draw, jot down notes of what you see and apply it later. It doesn't always work, and again, time is your best friend sometimes. Again, this is more of a fine artist approach and perhaps a bit too new-agey for you, but sometimes it's best to just sit down and face the block itself. Talk to it, look at it objectively.
Why are you unhappy with what you're creating? Where do you think root of the issue lies? Are you trying to solve a creative block with an uncreative solution? Find what you think the problem is and attack it. If that's not it, try again. This is coming from the outside looking in on more than a few career fine artists, so it could be completely wrong or partially right. Not quite entirely sure myself lol. Good luck, though. I'm sure you'll get back on track.