With the hype cooling down there is actually a LOT wrong with smash 4 if you ask me
-the UI is absolutely terrible
-CPUs are rather bad and will sometimes just brainfart (I had an Olimar throwing pikmin at me while I was far out of reach for a good 20 seconds)
-as soon as you turn FD mode off way too many stages have fuckhuge stage hazards or walkoffs. Some stages having these is fine but it gets annoying after a while during 4p multiplayer. melee and brawl had stage hazards and walkoffs as well but they also had relatively simple stages like hyrule temple and fountain of dreams. Variety is what you need for multiplayer.
-some of the items are very unfun, like the blower which gives basically no chance to fight back and the skyward sword beetle thing that just oneshots you
-much less 1P content than brawl and melee: no SSE, no adventure mode and no missions
-they kind of phoned it in on some of the characters' movesets, mostly with too many characters having a counter
-A lot of final smashes are copypasted from other characters, I don't think any new character actually has an original smash
-the bomb minigame is too similar to home run contest and not half as good as break the targets (although BtT already sucked in brawl when they gave up on making character-specific stages)
-the challenges are mostly just grinding while in brawl they were actual challenges
-quite a lot of loading time
-some strange design choices like not being able to buy custom moves with the ingame coins and changing character in multi man smash bringing you two menus and loading times back while it doesn't do that in home run contest
With all that being said, the core of the gameplay, namely the characters, are the best they've ever been. Lots of variety offering different playstyles and generally very balanced; while some characters are clearly better than others, there don't seem to be any brawl meta knights or melee pichus so far. It feels like, just as with melee and brawl, development ended up being rushed, and while in brawl and melee this ended up worsening the characters, in smash 4 they made most of the characters first and then cut corners on the content. Which I guess is a good thing, but I still rather had wait another half a year to fix some of those issues.