Ovechkin was on a 44 goal pace last season and is the active goals leader in the league. Yes, players decline over time. But seems like an odd player to compare a legit GOAT contender to, when that player is still performing at a very high level.
For a recap, Clarkson ended up struggling with a series of injuries that prevented him from getting to the peaks he reached in the couple years prior to his big contract. He wound up never fully recovering from those injuries and couldn't get back into NHL lineups consistently. Ovi on the other hand has been healthy most of his career, and doesn't play a style that would be likely result in career ending injuries. So again, I just don't see the Clarkson-Ovechkin parallels.