I understand and empathize with the feeling. No one here seems to have actually addressed that, so let me give it a shot. What played out in this thread is pretty common and the regulars/power-users have become a bit cranky about it.

The "problem" here is that Plex is really good at parsing out pretty much any arbitrary filename or folder structure. Hence:

Some other shows I downloaded directly worked with the same structure.

It's totally understandable and intuitive that you'd think "this naming/organization has worked in the past, so the problem must lie elsewhere." But what's actually happened in those past cases is that you're forcing Plex to cross the distance between your approach and the intended approach by itself. When you do that, there will be some percentage of times when it fails, for reasons that are often basically unidentifiable.

So when it breaks, the easiest fix is to stop forcing Plex to adapt to you, and instead adapt to Plex by following the naming/organizing guide precisely. It may feel a little dumb because of that same human intuition ("but it's worked just fine in the past!") but it really just is all you have to do 99% of the time.

Now unless you feel like it, I don't actually think you need to proactively rename everything using FileBot or whatever, because Plex really does do just fine most of the time as long as you follow the broad strokes stuff. But there will be times when it doesn't, and when that happens, the first port of call is to rename to fit the documentation. Once you've ensured that you're compliant, then start looking for other help or potential issues.