It's the dearth of really good tall fighters in the last 30 years or so, and it is clearly more visible now. Klitschko is a great fighter, but the competition is simply not there anymore for a fighter this tall. I have no doubt that if you threw him into an era like the 70's, where you had tall fighters like Foreman, Holmes, Lyle, Norton, etc.... it would've certainly tested him more.
Even the journeymen of that era were better than the name heavies out now.