But it wasn't as bad as many people would have you believe!
1. Class Balance: I can buy the argument that the classes might have been a bit too balanced and that too much damage looked like damage from any other class but... Fighters and rogues weren't useless at higher levels. In most versions of Dungeons and Dragons, once mages get past a certain level, really, why do you need a rogue in the party at all? Rangers didn't cast spells. I was so disappointed to see rangers casting spells again in 5th edition. This pain is only amplified by having the various Lord of the Ring movies with the very archetype of Strider out there never casting spells and then having someone trying to recreate that going, "Yeah, not happening."
2. Alignment. So wish they kept the simple stuff: Unaligned, Good, Lawful Good, Evil, Chaotic Evil. Alignments in 5e aren't almost worthless but worded very closely together...
3. Minions. Monsters that might be of a certain power level but were not meant for long running fights? Mind you, given how long fights in 4e tended to be, and how underutilized minions were, I don't think this every fully shone through, but fun stuff there.
4. Fey and Shadow Planes: Heck, I think that it was wise of 5e to snag as much as they could of the 4e setup there. The Shadowfell boxed set had a lot of great mood and elements to it despite the box itself being a cereal box and not an actual gaming box.
5. The Mythology. Yeah, a bit generic in places but I thought it was cool. Some of the new gods, like the Raven Queen really struck out. I also liked the Scarred Lands back in the day. They were even able to tie the new mythology into the Revenge of the Giants, a nod to the old classic. It made sense in that the giants in 4e were tied far more into the elements with some variants than previous editions did.
6. Digital Tools. I prefered it when they were downloadable but grew to grudgingly accept the online needed portions. The DDI made having a host of gaming material not impossible to handle.
7. 'Evergreen products'. Remember when the tile sets first came out and would quickly go out of print and be on sale at Amazon for like $100? And then WoTC said, "Hey girl, we love you. We're going to keep certain tile sets in print all the time and they'll be like, the most useful ones ever." Surprised to see that as of now, Amazon still carries them and still has a good discount on them.
8. Fixed Hit Points and ability scores. I know some people hate them and I understand that. There is a thrill in the randomness of rolling those numbers but in my many, many, many years of experience, the real differences tend to be towards characters who are so powerful that they never could have been made via rolling and "Such Luck" as the old meme dog would say.
9. Setting: While this ties into the mythology, there was a 'feel' that the new edition was going for; Points of LIght. Such a compelling idea that Goodman Games made not one, but two sourcebooks about it!
10. Running Encounters Rewards: I received a few freebies for running numerous adventurers at one of my friend's stores. This included miniatures, maps, and modules. It was a very nice thank you for running a game. On one hand, running a game can be fun. On the other, running at a store with people you don't know on a time you might rather be doing something else? That's almost like work and well, it's better to have some incentive than a pat on the back and your elderly aunt whispering that if you don't do it the future of the game is doomed.