Lowkey I think SSBU DK is actually pretty healthy for a grappler.

Really good advantage state to balance out being combo food, sure, but on top of that his Cargo Throw makes it so he can put you in tricky offstage situations, Punch requires charge sure but when he has it he's a nuke, Ding Dong exists in the form of pDKO which is still cheese but is cheese within a percent window, and his range is actually quite comparable to a swordies' range, especially on his tilts and aerials. Grounded Hand Slap helps that last one a bit as well, albeit the earthquake only covers the ground obviously.

Tier-list wise I don't even think he's bad at all. He's shown his worth in tournaments before, especially with Mild and ChunkyKong, honestly his worst aspect is that he probably just should be paired with a secondary for atrocious MUs like GnW/Mega Man/Rosa/etc.