Also, I try to use plates as little as possible because then I have to practice lightning etc a bit more.
I'm not sure why you think this is true. You are producing a huge amount of work, and some really nice looking images are coming out of it (as well as some not-so-nice ones) - but I think overall you have a slightly unrealistic view of how mattepainting works.
If you are doing this as a hobby, then trying to work in a professional manner doesn't matter (and will probably make the process less enjoyable). But it seems you are trying to work towards mattepainting (or at least CG) as a vocation.
The process of mattepainting in a professional setting is NOT:
Find some cool photos > put them together > see what you can do with them > make a great image
And more like:
Start with a clear idea of what you are trying to do > work out how you are going to do it > find the relevant source photos > do the work
I know you might think you have got lots of contradictory advice from people on this forum, but most of it has been pretty good direction. The initial work you were doing was too small and obvious (and hence easy) to be particularly good practice. Your recent stuff has been very ambitious work, but without any clear goal other than to get a bunch of photos to match.
You've definitely had successes (one of your snowscapes in particular is beautiful), but it looks like it turned out beautiful by a bit accident rather than purposeful design.
You've got a great work ethic and a huge amount of dedication, both of which are very impressive. If you could direct your energies in a more focused way, I think your work would massively improve.
You don't have to do this, obviously, but here is an idea for your next painting:
Take a photo of your street, or a bunch of buildings in your hometown in bright sunlight (bright enough to have obvious shadows)
Clean up the scene - make it look like a picture postcard - the perfect street. Remove any dirt, clean up the edges of the road and any grass, paint out the weeds, maybe add a blue sky (though subtly enough that the shadows still make sense)
Then do another version of exactly the same image where the street is derelict. A ghost town. The windows are smashed, there are plants growing up through the asphalt, and the doors are shuttered.
Don't change the light direction or the length of the shadows in either painting - the challenge is to change the atmosphere WITHOUT changing the lighting.