DDD's only problem is that he is such a fattie.
Other then his size he really doesn't have too many weaknesses to abuse.
People think he is bad because of how susceptible he is to combos, but he has so much going for him despite that.
His tilts are all great, like almost Snake level good.
Ftilt has freakish range, quick, and cancels out a majority of the game's projectiles. Its great at poking and stopping aggressive approaches.
Dtilt is very fast, good range, and a great GTFO move. It even edgegaurds fairly well from the stage, though he has an even better offstage edgeguard game.
Utilt is only outclassed by Snake's Utilt. The gravity increase kinda screwed it over like it did with Snake's but it still kills well, it is reliable, and fast.
His aerials are also great.
Fair has good range, fast, great for WoP's at low to mid percents, he can now combo into it, etc. It was good in vBrawl, and IMO B+ made it even better.
Bair is just a machine. It edgegaurds exceptionally well (I still say DDD's Bair > some characters all on its own because of how well it gimps). It kills surprisingly well (towards 140%ish iirc). It's one of those stupidly high priority moves that just doesn't stop dishing out pain.
Dair has been functioned into a great combo move. It does suffer from SDI syndrome along with other multihit moves, but it when the last hit connects it sets up for his other aerials beautifully.
Uair can combo at lower percents, and he can reliably combo into it. It kills rather well, and the only real problem with it is that its a multihit move so again SDI is the bane of it.
Nair could actually combo in vBrawl at low percents, so imagine how well it works with noticeable hitstun. FF Nair is great, and can combo into Utilt, grabs, Usmash etc.
He has a good, reliable projectile that can easily force most characters in the game to approach, and the waddles serve as mini sandbags for absorbing projectiles that fire lower to the ground. The chance for a Gordo make it even better.
His neutral B (swallow) has super armor which allows him to stop approaches and deal extra damage. Landing a suicide isn't all that unlikely either.
His recovery is great, though when he is forced into his Up B then he can be put into a bad position quickly. However, more often then not DI and multiple jumps is all he needs. Multiple jumps also allow him to defend himself offstage without too much worry as to not being able to recover after.
And his grabs are still amazing. Uthrow is a great combo throw now, Dthrow sets up for tech chases, Bthrow does 16% which racks up damage very well considering how often DDD lands grabs, Fthrow is the only meh throw but it does setup for edgeguards so it isn't useless.
DDD just has next to nobody playing him. People just tend to prefer the faster, more combo oriented characters in B+. It's understandable I guess, but I don't think by any means DDD is bad. He isn't the only fattie out there getting ***** by combos, and he has just as much (well more really) going for him then a character like Bowser or Ganon.