It's getting worse in a bad expansion when we're deep into 8.2.5. This isn't a case of faction balance, even though there are more horde than alliance. It has to do with the fact that people are bored with EP and more specifically, bored with the entirety of BFA. Again, this shouldn't be an issue in 8.3 when people return and 100% won't be a problem when shadowlands launches. The beginning of expansions never have issues with players. Besides, this only affects mythic raiding, not raiding as a whole. I haven't done a single heroic raid with people on my realm since week 2.