While I agree with this, a) that's on the player, because he can probably opt for a shorter deal that constantly requires resetting (i.e. the Kirk Cousins effect) and b) there's no logic behind a team signing a player to an extension that's based on perceived market value 3-4 years later.
Honestly if Lamar came out and said "hey I only want to do like 2-3 year deals at a time", so that he can perpetually reset to market value, I'm fine with that. I don't think the FO will like it, but I think they'll do it anyway.
But if Lamar is as smart as he seems, he'll also know that the shorter the deal, the less cap flexibility there is, and therefore, the less likely it is that the "talent" around improves dramatically outside of the draft. If people want to see how "real" the salary cap is, start signing all your players to max, fully guaranteed, 2-3 year deals. I bet you'll see how little wiggle room there is then.
And for all I know, length may be a sticking point too. I'm sure the Ravens want long, and I'm sure Lamar wants shorter or middle.