No. It’s highly likely your admitted increasing dislike of Clint Eastwood might be colouring your own opinion of the picture (and I understand that, btw: I’ve found James Cameron to be such an unlikeable prick in so many interviews it’s coloured how I see many of his films). It may also be that, irrespective of how you may feel about Mr. Eastwood, you just don’t care too much for TGtB&tU which of course is fine too. No movie on Earth is for absolutely everybody.
But The Good, the Bad and the Ugly is most certainly not being overrated. It really is one of the finest movies ever made.
For my part, I don’t especially care for Once Upon a Time in the West. I mean, I do like it but it just scrapes in to my own spag top 30. However I think it would be churlish of me to assume that everybody else is overrating it. I’m just not as keen as most, that’s all.