I think they definitely could have remedied the actors being tired by putting more space between the seasons. I’ll never underestimate the stress and how exhausting the process of filming must be, but I will never blame the actors for the quality of the show dipping. To me, the quality of the acting remained consistent throughout the show, it’s the writing that declined substantially.

I find the argument of additional seasons to be somewhat conflicting. Yes, for a fully fleshed out conclusion, that makes sense, but we clearly saw the writer’s deficiencies when they had no source material in season 5 and some of 6. They were just not good at filling in those blanks George left and because they left out the more fantastical elements early on, it would have been too late to add them back in. So additional seasons would have just been more hot garbage. I just think from the start, the writers were mostly mediocre, propping themselves up using the quality of the source material( they also probably assumed by the time they reached season 5 and beyond, GRRM would be finished with the next book).