It's insane?! What does he do well? He does nothing well is the answer.
He skates decent for a bigger guy
Has long reach because of being big, not sure that even counts as a plus
Doesn't provide offence
Doesn't protect crease
Doesn't protect teammates
Has zero physicality
Struggles like many Wings D to make easy plays to get the puck out of are zone
Just like Jensen, I think lots of people on here are overdoing how good our decent/ok players really are. Jensen is not even someone I would want in my top 6 at any point, unless you had half of your top 8 guys out.
Jensen is a solid player as is evident by being a mainstay on one of the best teams in the league.
Your criticisms against Dekeyser seems to be 3 versions of "isn't physical enough for my tastes". He's a good defensive d-man. Skates well, good reach, good defensive stickwork, decent at clearing the zone, decent first-pass kind of guy.
He's not great offensively but you can't just make a blanket statement like "doesn't provide offence" either. Last year he had 20 even-strength points in just 52 games. That's more than Kronwall, Parayko, Girard, Bouwmeester, Fowler, Chychrun, Vatanen etc. had, and the same number as Doughty and Subban had, and Danny had less games played than all of them.
Oliver Ekman Larsson had 2 even strength points more than Dekeyser, in almost 30 more games played.
Sure Danny has been inconsistent with the offence, and he's not someone you really want on a powerplay, but you simply can't statistically back up a statement that implies he provides no offense at all.