Trying to take away from his win against Mendes is simply disingenuous. McGregor had a hurt knee, and was training for a completely different type of fighter than Mendes. Allegedly he wasn't even doing any wrestling in that camp, and yet he still used his grappling to either stuff or escape, then knocked Mendes out. Neither guy was at 100% but McGregor came out dominant. Like you I've been following McGregor since long before his UFC debut, and the criticism has gone from "McGregor has never fought a wrestler" to "well, McGregor has only fought ONE of the best wrestlers in MMA history". His wrestling has been tested by very good wrestlers, and one elite wrestler, and it's held up. Beyond that, he's outboxed everyone he's ever fought--including Diaz (seriously, who else has done that?).
Edgar would have been a great test for him. Lamas not so much, I see no reason to believe McGregor wouldn't handle Lamas, who's lost to every elite fighter he's faced and been knocked out a couple times. Hasn't shown the best wrestling either, nothing close to the takedowns of Mendes or the striking skill to set it up.
There are question marks around every fighter. Jones never rematched Gus and is a juicy slut, Mighty Mouse is beating up midgets nobody's ever heard of, GSP greased, the list goes on. If you put anyone under the microscope you can start discrediting their wins, raising questions, coming up with guys they never beat 5 times, whatever.
At the end of the day, the point is that yes, just like literally any star, McGregor was built up. He got some favorable fights. He also got some shit fights, and has taken extremely tough matchups on short notice. He got a title shot he didn't deserve, but so have many in UFC history who I've already named. He's been holding up the title, and I'm as pissed about that as anyone, but that doesn't affect his in-cage performances. He's going down in history as the thread two weight champ and one of the biggest stars the sport has ever known because he backs the hype up.