Unsure about both these statements.
I kind of agree with you about the level of challenge Silva has had, but he's made them look bad as well. It's a tough question. But before the juicing thing (which puts a question mark on his other fights) be could have been considered a GOAT. He toyed with the guys you mentioned, and put on great performances against a fighter with a style that was supposed to be his kryptonite (Sonnen).
And yes, DC got outclassed vs Jones... but then again, what did that fight really mean given recent events?
Only fight I would say Anderson fought with a style that's his kryptonite would be Hendo. Sonnen utilize wrestling as well but he is so limited in rest of his game to really be considered as his kryptonite. Nobody considered Sonnen to be a tough stylistic match up for Anderson, that's what made the fact that he controlled him for 4 rounds impressive. Keep in mind, this is the same Sonnen that got triangle choked by Babalu and hail-mary armbarred by Paulao Filho. Maia ran a grappling clinic on Sonnen.
For someone who's supposed to be GOAT, Silva had really limited offense off his back, he wasn't as imposing in terms of striking (Maia, Leites). The guy he toyed with were all average strikers who were billed as great ones. Nobody categorized Bonnar, Griffin, Irvin, Cote as great strikers. Why should we care that he beat these guys? When Silva moved up to LHW, guys like Rampage and Chuck were still around, and beating those guys would make a much better case for him than the guys that he fought.
Just my opinion, I still think he is a great fighter, one of the best of that generation. And again, I am only comparing his reign to Fedor's, as they were both considered GOAT from that era.