With Netflix I feel like it's the opposite even - you have to just force yourself to stop watching any of their originals after 2nd maybe 3rd season at most because it always, inevitably ends up deteriorating in quality massively. I don't know or even have a theory as to why that happens, but so far it has held true for me.

Here's my theory!

Perhaps the writers write the first season fully aware of the probability that they won't be asked to write a second. Then, when it's a surprise hit, they are less sure of what to do following the events of the first.

AFAIK, Netflix decided that they only were going to make 2-3 seasons at most, and only locked up talent for that long. Therefore, some behind the scenes changes after season 2-3.

I don't know whether that's still their assumption.