I'm going to be that gigantic douchebag who asks the obvious question instead of doing the bare minimum amount of research: why is 5e considered bad? I blindly assume it's due to critical role dragging in the Twitter crowd, as well as everything Hasbro touches being complete shit as a strict rule.
The issues with 5e can be separated into "5e, the system" and "WotC's 5e output"
My issue with 5e, largely, is that it has all the issues of 3.x and 4e, and discarded almost everything that was an advancement from 4e.
There's some good shit in 5e; I like advantage, they have a decent fear mechanism that doesn't remove player agency like PF, I like the resting mechanics, HD are better than surges, allowing a single "bonus action" with the option of giving up move/standard to get more. Allowing average rolls for things like HD in the RAW is also a big plus in my book.
What I hate is the spells have the same power creep as 3.5 and the endless & unbalanced subclasses. I really hate saying no as a DM, but for 5e I toss more than I keep or the game just goes stupid. To keep bitching about subclasses, there is no subclass trade off they are only additive. Which on one hand is good, you don't have to think about fucking over your character for a choice you made at lvl 1. But its also really bad because people just google "Best 5e subclass" and everyone makes that subclass because its easy to see that it is the most powerful.
Over dependence on skills. I am not against skills - you don't have all your senses, players need some help. But 5e adventures trains players to overly depend on them and to not think critically, because thinking is abilist, racist, and gatekeeping.
Also Crossbow Expert, and the return to infinitely stacking bonuses.
Mainly it just feels like for all of the multitude flaws 4e had, 5e feels like a step backwards in terms of layout and playability.
Then there's the issue with WotC output.
4e did a lot of tomb looting with adventures and ... I don't know if you can call them splats when they are hardcover... supplements that were revisits of classic settings like Tomb of Horrors. But they weren't module reboots/reskins, they were very clearly to take place after adventures from an earlier age had been through.
5e straight fully reboots the settings it revisits to be as woke as possible. It destroys them, full "Year Zero, the Past is dead". Which wouldn't be too bad (minus the woke) except 5e goes back to the 3.xe model of allowing nearly direct conversions. Conversion of something like Ravenloft to 4e takes a little doing as you need to convert items and monster abilities to 4e action economy & power levels. 5e maps almost directly, there is no need to do a woke retooling of Ravenloft except as a cash grab.
So while 4e sort of exhumes the sarcophagus for display in a museum, 5e flays the corpse, puts on "Goodbye Tarraraques" and dances around in the skin.
Then, Like
@Adamska says, the system almost from release started to tear itself down. It does this really annoying thing by using vague terms in feat & spell descriptions, but then going out of its way to remove GM agency to rule on things it doesn't make clear. The GM is expected to Arbitrate what "Power over wind" means, but deciding if Orcs are murderous or able to integrate into lawful societies is simply beyond the pale.
On a related tangent,
I know I have grognarded about Theater Majors shitting up games, and critical role making people think they should play the wrong sort games, and what I'm about to suggest would only making it harder to try to get a group of people together "to play D&D" by making the definition of D&D even more over broad than it already is, but...
They really need to bring back Basic and Advanced D&D.
They really need to segment out the crunch and let you pick and choose what you want to matter.
I know you can home brew some of this shit, but when I am buying into a system I'm not paying to be told how to roll dice. I'm paying for playtesters and people who are good at math to have given me a model that maps to real world expectations but is more fun and doesn't explode when you find the edge cases.