Conleth Hill has been very outspoken about being disappointed with the last three seasons, over multiple interviews. You're right that we don't know what he was thinking in this moment, but it's absurd to call it "heavy misguided opinion" given the weight of corroborative evidence.

“I suppose the last couple seasons weren’t my favourite,” Hill admitted. “That’s fine though. It’s the nature of a multi-character show,” he continued. “It was kind of frustrating. You can’t help feeling that you failed in some way, that you haven’t lived up to some expectation that you didn’t know about.”

You're welcome to disagree with him, but ignoring his statements in order to pretend he, and the other cast members who've explicitly and unambiguously expressed their disappointment (Joe Dempsie, Nikolaj Coster-Waldau, Emilia Clarke), is a pretty fruitless endeavor, to say nothing of the cast members who've couched their disappointment in humor or ambiguity (Peter Dinklage, Kit Harrington, Isaac Hempstead Wright).