I agree, with some minor differences.
I thought Seasons 1-4 were not perfect-- there were alot of little things that weren't executed that well-- however the overall structure of the season and focal points were very well planned out and for the most part, executed very well. As a result, when you look back at the seasons, you tend to forgive and forget the less significant flaws and you tend to remember the primary beats that do in fact feel right/massively satisfying. Season 1 and 4 were PACKED with these perfectly pulled off focal points, which make them feel close to perfect, whereas seasons 2-3 had a handful that were placed in exactly the right places.
Season 5 was lame. I legitimately think it was a mostly mediocre season (with a handful of good moments), not only based on the standards set by GOT, but also by the standards of other examples of "good television" set by critically acclaimed shows these days, IMO. It seemed to be making mistakes that other shows that are intended to be serious efforts wouldn't be caught dead making. (The Sand Snakes were far worse than anything on Daredevil or Mr. Robot, for example)
The "it only looks worse because of the standards set by GOT" thing I actually think applies more to season 6. It's fine, it's solid, and it's good entertainment, but it has not been anywhere close to S1-4. It feels a little rushed, a little bloated, a little overreliant on action sequences/exciting plot developments/deaths.... Not necessarily unfocused, but not as sure-handed, intriguing, and artfully built up as S1-4 for sure. Still enjoyable and a massive step up from 5, though.