Very little character customization. The feats are better, but you might not get to take any because you have to choose between feats and ability score increases. This is for the sake of making feats optional, to pander to grognards who don't want even that amount of customization. You're best off playing a caster because they don't need feats as much. And you can't make or even buy magic items, so past the first couple levels your wealth is just a number that goes up without doing anything you care about.
This is nonsense. Theres enough character customization. More than enough if you mean to multiclass. Feats are optional, but important nevertheless, if you want to skip attribute increase you can. The problem is that you are so used to array that they idea that you could end up with good enough rolls thanks to rolling dices isnt even in your mind.
Also its solid character customization, not the retardation that we encountered in 3e where the system was broken beyond recognition in the PHB, everything that came after that was just adding insult to injury.
Untested low quality content to fuck your game further.
Finally you dont actually need to plan your character in thsi edition, that means players that arent rule lawyers can actually end up with a working character instead of pure garbage. The difficulty of the system isnt in building a character, any retard can do that, the difficulty of the system lies tackling any given encounter with your character and how youll do it using the tools at your disposal.
Lack of tactical depth. In 3e you have charges, flanking, 5 foot steps and the like to keep you moving in combat and encourage teamwork. In 5e you just walk up to a monster and hit it til it dies, like you're playing an MMO. If you want to do anything else, you'd better be playing the fighter archetype that can do combat maneuvers that anyone in 3e can do. And there's nothing like the Tome of Battle that makes martials fun.
Plenty of teamwork in 5e actually, lots of abilities rely on allies. The deal with the system being more narrative is that it allows you to be more creative with your tactics too. Also there are 5 foot steps, they are called disengage action. There is flanking, it gives advantage, If you want to charge all you have to do is turn your action into a movement action and move twice on the same round.
Also in this edition these things actually matter, in 3.5 positioning and everything else got fucked as soon as the mage learned fly and invisibility.
It isn't even a finished game. It claims that its "three pillars" are combat, exploration and social interaction, but they only bothered making rules for the first one. The rest of it is just "the DM makes something up", so if you want anything but hack and slash you'd best look elsewhere. 3e gives DCs for common skill checks, in 5e it's all something the DM pulls out of his ass. Want to get an idea of your character's capabilities out of combat? Too bad, it all depends on how much the DM likes you.
Ah yes, 3e skillchecks, the ones that got increasingly bloated as the campaign went along. Nevermind that the entire thing was broken beyond recognition because you could inflate your skillchecks to high heaven and never fail. The alternative was ALWAYS fail.
Anyway, if you really need help, then DCs arent terribly hard to implement, easy difficulty starts at 8 and should cap on hard at around 20.
As for everything else, the DM can handle it, thats literally his job.