He is comparable to Boonen, but was midguided unfortunately.Sad to say this, but he's wasted his best opportunities to win some more titles, some, from his mistakes, some from reasons he could not affect. For me, the biggest mistakes, his and his managers were, when they tried to make him a better climber, where actually after each episodes, he ended up a little bit lesser climber then before the experiments. And they tried it in cannondale, in tinkoff and in bora too.
Ont the other hand, I don't think, he's that old. He's past his peak for now, definitely, but it has nothing to do with age, imho. Not so long ago, he would be in perfect age for longer classics. It's just that, like he dominated in young age, currently there are other very young riders, who are maybe even on bigger level that he was at their age, it's just that simple. The young guns are out of the world currently.