ANyway, I don't htink I've acutally made a list of my gripes with 5e.
So, here it is. Note that most of these aren't things I think 5e got wholly wrong, and 5e is my second favorite variation of DnD.
Advantage: I like it, but I think they miss stepped by having there only be one bonus, as it were.
Trying to put "4e style" gameplay in a "tactical play" module in the DMG. It's a failure, IMO. I don't know what the numbers are, but not a single person I know who liked 4e wanted to play a game that mechanically resembles warhammer. At all. That isn't what 4e is, and while it's cool to have as an option, it is not a 4e style option. 4e's "thing" was tactical options built into class abilities. Not...facing.
The art style. The conceptopolis stuff is great, mostly. The halflings are an abomination. They look like gross cartoon people halfway turned into real people. I feel like they're going to plead with me to kill them while the artist isn't looking.
There's some great art from 4e, like this:
http://img.photobucket.com/albums/v229/JonasAlbrecht/Gwenn.jpg that is vastly more interesting than most of the art in the 5e books. Or stuff like this from Jon Hodgson, who does the art for The One Ring rpg:
http://jonhodgson.deviantart.com/art/Solku-119883066
Not having more "modules" for more complex play in the DMG. Bigger weapons table with more weapon properties, for instance.
Not putting out some pamphlets for the more popular non FR settings, or a book with info on multiple settings, maybe with worldbuilding advice from setting creators like Keith Baker, etc.
No digital tools. I've heard this isn't really their fault, as bad luck struck again, but they need to stop messing around with companies no one has heard of, and figure this situation out for real. Either develop a department of digital production, or work with one of the companies making DnD video games/mmos.
Maybe hire some talented app makers who have made char builders for various editions, and give them the money to do it right. Heck, allow digital tools on the DM Guild, now that that's up.
Not allowing there to be both class and subclass iterations of ideas. IMO, this would open the game up without unbalancing it, and allow certain concepts without MCing, etc. If you have to, put the class versions of things like assassin and any given summoner/pet concept in a special area of the rules called Advanced Options or something, to satisfy the grognards and the folks who hate there being more options.
Like I said, none of these is a big deal, really.