The distributions of their strengths seem quite different to me, so I don't think the comparison is very meaningful, nor do I think it's true that Evenepoel is quite a lot better (as a blanket statement).
It's about as meaningful as compaing him to Bambi. It's trolling 101 but some people find it funny, and that's basically where it ends. Spilak did not win one ITT in his pro career. The joke is that he was "good at one week stageraces" but not at GT's. Evenepoel only did one GT so far after a big injury and messed up winter preparation, but the jury has decided. Spilak in his entire career, won 3 one week stageraces, counting the one won by Valverde before his suspension (which by your logic in the GT podium topic, shouldn't count). Evenepoel, at age 22 after missing the better part of a year due to an injury, has already won 7, with maybe later today his 8th. Evenepoel already has over double the amount of pro wins and more medals at WCC than Spilak had after retiring.
Is he as of now a better climber than Spilak? Can you say that he isn't? Or just that you don't know yet. Evenepoel bonked in the last 1.5k in the first climb in early february. Is that the sample size you want to make that call? Picon Blanco doesn't count? How many times did Spilak bonk? Not that i'm a big Spilak connaisseur but i'm thinking quite often, or he would have been better at GT's. With Evenepoel the argument always steers towards his failures, which are then compared to other riders' successes. There is always some reason why his successes don't count.
Spilak didn't win his GC's against Contador or Froome. He won them against Kruijswijk and Dumoulin (before he became a GC rider). He also quite frequently bonked in one week stageraces, while Evenepoel has won nearly 50% of the one week stage races he entered.