Ding's problem was not his time management but his mental game. It's no secret he's been struggling for the last ~12 months and he admitted as much that he didn't prep well for this match. Having said that, the guy got himself into favorable positions multiple times and then was happy to trade-off pieces/repeat moves to get the draw.
The last game was where he took it a step too far. Several times during the game he had the opportunity to pressure Gukesh to find the correct sequence of moves, only to take the easy way out and trade a piece to make the game more drawish.
His blunder at the end was him thinking he'd just trade off the Rooks and kill off the game, but missed the fact that he basically sac'd his Bishop in the process.
This is so important, and people who watch games with engine eval or with commentators who use it don't realise it at all. Often in a chess game you're looking at a position and going "am I even ahead here?"...and when I do an analysis of my own games I'll often find that my own sense of the position doesn't at all agree with an engine evaluation. Clearly the situation is going to be much harder at the elite level where the edges are smaller and doubly so in this particular world championship where the positions were generally extremely complex and double-edged.
But I think that just comes back to his mental game/lack of match prep. The Ding of 5 years ago that pushed even Magnus Carlsen wouldn't have been out of prep 5-8 moves into every game and could've afforded himself more time in the mid-game to find the advantage.
It's basically what allowed Gukesh to do exactly that throughout the match. His opening prep was impressive and because he allowed himself time to think outside of the opening he at least tried to push on most games.
The last game was where he took it a step too far. Several times during the game he had the opportunity to pressure Gukesh to find the correct sequence of moves, only to take the easy way out and trade a piece to make the game more drawish.
His blunder at the end was him thinking he'd just trade off the Rooks and kill off the game, but missed the fact that he basically sac'd his Bishop in the process.