Definitely not. Dedede is really bad overall, with slow moves that make for one of the worst neutrals in the entire game, and poor hitboxes on some of his moves, such as nair. I think Dedede is among the worst of the cast, though that doesn't mean he's lacking completely. It's Ultimate, where even bad characters have enough to succeed now and again. Additionally, if you played online, that buffs Dedede tremendously. So that is probably why we differ so much on our feelings towards him.
If Ganondorf wasn't so bad, I would argue that Dedede is the worst heavy. Charizard is fast with a ton of kill options, Incin's entire kit is excellent moves plus Revenge to help his disadvantage out a lot, DK is fast with swordlike range and a great combo game, K Rool has armor and projectiles that aren't as detrimental as Gordos, and Bowser's entire kit is excellent moves backed up by being fast. I think Dedede pales in comparison to all of them.