It is no fun, but like @tom80H said, there are some naming and tagging rules to follow. It is especially vital that the Album Artist tag is the same single artist name for every album, and if it is a compilation it must be the magic word “Various Artists.”
It’s possible that after you update your filenames and tags and rescan it still might not look right. You should either do the Plex Dance with the changed files, or actually delete and recreate the library. I find the latter to take less time, just make sure you turn off Sonic Analysis and all the detailed metadata features until you know the basics are working correctly.
A program like mp3tag will make huge naming and tagging changes pretty easy once you get the hang of it.
