Here's why I think he's terrible:
-Bad projectile (can be swatted back at him by almost anything)
-Slower
-Still fat. Still a big target
-No fast aerials (unless you count nair, but the lack of range and the ending lag are not even worth it)
-Reduced grab range
-Almost no approach options
His bad projectile, bad attack speed, and bad air game make it hard for him to camp or play offensively. He has no safe playstyle IMO
All very valid points. His aerials aren't very good on-stage besides their usage for followups after dthrow. Though I feel nair is worth using it if you fastfall it, and it's my most common and reliable way of getting back on the stage if I'm above the stage. The hitbox itself is small, but that doesn't matter with Dedede's insane fastfalling speed.
Hitting the Gordo back is something that hurts us, a lot. Because of this, I never really use it as a conventional projectile anymore. I now commonly only use it to stop any approaches towards me, while I slowly work my way to my opponent. You can send it at a vertical bounce by holding up at the end of the side-b. Making it a very threatening and somewhat unpredictable wall.
Dedede is heavy enough to be able to eat a few projectiles, and I use this knowledge to slowly approach my opponent, never really commiting to anything laggy on the way the opponent might punish even if it'll cost me 10-15% just to get there, approaching in a greedier way will just cost you more. You need to be patient approaching with Dedede, as his dash attack is awfully slow and only really good on people that like to spotdodge on the edge or other weird stuff. Pretty much the only out of dash options he has are shield and grab, and the rest is just going to get you hit.
In general. you kind of want to keep your opponent around your f-tilt range with Dedede, and angling Gordo's upwards really helps doing this as you move towards them. I generally just keep slowly edging closer until my opponent has to approach me or eat an ftilt. An advantage of Dedede's fatness is he's so big it's kind of hard to get past him if you play it right. When they finally do approach or try to get past you, you have a lot of tools to punish them, possibly getting them off-stage and then continue to keep them there with angled Gordos, ftilts, grabs, and all your heavy hitting aerials.
His grab range is just 'normal' now, it really needed to be nerfed because it was just ridiculous in Brawl.
But because of all this, as I said before, he does very bad against characters with good keepaway games. I still don't feel he's bottom tier, as I've had a lot of success playing him roughly the way I described before. On top of this the game is generally being a bit more favorable to heavies than previous smash titles, with the further blast zones and rage mechanic. Give him a shot with this in mind and you'll find he's really not as bad as he might seem, he's just very different from his Brawl iteration.
Sorry if I'm making it seem I'm only here to protect Dedede. I used to play a lot of Olimar and I was wanting to give him another try in this game after everybody seems to say he's pretty bad. I'm really hoping there's some way to make him work.
I actually feel like Olimar is better in some ways. He's still my best character, and I'm doing just as well with him as I did in Brawl. The lack of Pikmin at first appeared to be a massive nerf, but everything still works in practice. Though his up smash is no longer reliable, I'm getting more use out of his grab game than ever before, up throw to aerial juggling works as an amazing combo on most characters. Pikmin Toss is still an effective damage wracking/get away move, and you can pluck out new Pikmin as quickly as you lose them. I've already fallen into the habit of tossing all of my Pikmin onto the stage before using my recovery, it often makes the opponent dodge out of the way so you have room to land, and if any Pikmin hit them, you'll get some damage in to boot. Really the only major complaints I have are him being a bit sluggish and his grab range being worse, but he's still a good character.
Does he still play the same as in Brawl? I tried playing him that way, but I'm really not able to keep people at range anymore with my Pikmin. Making me unable to really punish anything to do. I never was that great on the offensive with Olimar. Do you feel you need to be more aggressive with Olimar now? Or am I just doing something completely wrong... I haven't played him a lot yet, because there's so many fun characters in this game I'm having a hard time committing much time to any single ones besides Dedede and Palutena because I kind of just want to play them all.