Aldo's one of the GOATs who never fell off skill wise. His skills were still great till the end. Hell, he's off winning boxing fights right now.
His only real loss that way was Conor where he did simply run into a better striker who could outstrike him. You can call a 13 second KO a fluke all you want, but the reality is Aldo was going to try and box with Conor and Conor was the better boxer. The result was likely going to be a Conor win, stop with the mythical leg kicking or BJJ Aldo that was never going to happen.
Aldo's problem with his other losses weren't skill related but cardio and fight duration related. Both of which had been problems all throughout his career. He was beating Holloway and Yan striking until he gassed, and Volk and Merab simply tied him up to waste out the only 3 round clock on him. Skillwise he was better than all of them but couldn't maintain it / have enough time to prove it.
Merab's really the only one of those I'd argue he'd have probably still lost even if he had better cardio and it was switched to 5 rounds as we know Merab could still just do that for 5 rounds even if it does give Aldp a better shot at landing something. Even if Aldo still equally maintains a perfect TDD all fight that's still a loss though, that's just the judging criteria that Merab pushing him against the fence for 25 minutes is still a win. Nobody would really walk away from it thinking Aldo's lost a step though as nobody else could attempt and fail 70 TDs on him.
But yeah, when Hominick rallied back to dribble his head off the canvas a decade ago I don't know how Aldo and his team didn't go full cardio mode. His skills were always elite, but he needed a better gas tank to utilize them fully.