Despite the issues in the latter half of the series Game of Thrones will go down as one of the greatest drama series ever. The Wire, Sopranos, Breaking Bad etc.
This highlights that shows, especially ones as gruling as GoT and the others listed, shouldn't go past the five season mark. No data or research to back this up, purely my thoughts.. but people tend to turn against shows, become too nit-picky, find flaws, once you get past that mark. Most dramas tend to peak in terms of support by the 3rd or 4th seasons. That's when it has some episodes behind it, word of mouth has gotten around and everyone is still in that honeymoon phase. After that it gets iffy. There were certainly a lot of detractors with regards to The Sopranos as the fifth and sixth seasons aired. The Tony Blundetto character and Tony's coma/dream sequence in the 6th season.
That's not excusing poor writing or hasty decisions in the 7th and 8th seasons of GoT (though season six gets lumped in here and it shouldn't it's great). But to me it's still high quality writing compared to most. The amount of nit picking I've seen done is amazing, people are just checked out.
I can't imagine the outage if Stannis suicided dived into an army of Lannisters at this point in the series and survived, especially seeing The Onion Knight show up alive later. No accusations of plot armor at that point.
My thoughts, as terrible as they might be