Trading Ovechkin isn't going to make the Caps horrible. He's a 30 goal 9 million dollar winger. Trading Ovechkin is probably going to make the Caps....similar to what they are now. Get rid of Ovechkin and replace his minutes with Burakovsky and Vrana, and they are probably similar or even a little bit better. The Burakovsky-Backstrom-Oshie line was miles more effective than that same line with Ovechkin, and you aren't even accounting for the players and depth 9.5 million in cap space can add.
Ovechkin has been a generational talent. But he's 32 and....not anymore. He's not like Sid where he's maintain/changing his game to stay as good as he always was, he's already declining. Ovechkin was the best pure goal scorer to ever play. But that doesn't mean he's the best pure goal scorer in the NHL today. In terms of goal scoring, I'd take Kucherov, Matthews, Tank, Laine, Pastrnak, Malkin, Rakell, Simmonds for sure over him. That's just the top of that list. And all those guys are far more effective complete players than Ovechkin.
This isn't about Ovechkin's legacy. This is about what Ovechkin is now. What he is, is an overpaid 30 goal scorer who is a liability 5v5. You can't keep building around him because his age and cap hit prevent that. When you have players contributing 2/3 of what their cap hit is, in a league that's increasingly becoming more cap intelligent, team building is HARD.