So, it seems as if a lot of people are pretending every season after season five doesn't exist. What's the deal with that?

I haven't seen anything quite as extreme as what you're describing, though I have seen people comment that they preferred the first five seasons. I can understand that. Those five seasons were the ones originally planned, and you can see it in how everything flows together and fits by the end of the fifth season. The newer seasons are a bit more made-up as they go along.