I rewatched it for the first time in about 10 years fairly recently, and it was still incredible. Was really worried it wouldn’t be as good as I remember it being, but it was.
And whilst the last series doesn’t stand up to the rest of it, it was actually quite a bit better the second time around. Might have been a case of diminished expectations due to knowing it wasn’t as good as the rest, but I now think it’s more of a case of 1-4 being so good that it feels like a big drop in quality when it would still be a very good season of most other telly programmes.