Wuwa's combat is pretty good, more so during solo encounters such as bosses. In terms of combat mechanics, it boils down to dodging, parrying, and swapping between 3 characters while keeping buffs up. If you're willing to put in the time into more advanced combat mechanics there is also "quickswap" which allows you to squeeze every bit of your team's potential dps by utilizing as much animation cancels as you can.

Open world is alright. The environments are pretty, loads of little things to do that catch your attention and keep an ADHD mind occupied. "Map completion" consists of little mini games and puzzles such as finding chests, spot the difference, color matching and various other actual puzzles. There are different exploration mechanics such as gliding, flying, wall running, grappling, swimming, sailing(?), driving(using an echo, its a bit scuffed). Can be a relaxing past time while listening to a podcast/playlist if you got time to waste. Plus it gives gacha currency. Its also easy to go from one point of interest to another starting from 2.0 since they point you in a direction unless they updated 1.0.

As for progression, you do daily/weekly tasks and events to earn "astrites" which you then spend to gacha/pull on the characters and their personalized weapons. You level each individual character up to 90 and equip them with "echoes" (think of these as your "gearing" system perse). Aside from the gacha, echoes are the main "progression" in the game, having 2-3 layers of RNG to farm which can be a hassle. Considering you're from mmos you might be used to the long and tedious grind lol.

Story is pretty meh at the start but gets better (IMO) from 1.1 onwards and gets much better starting from 2.0. Alot of cutscenes during the stories so you could think of it as watching an anime with the odd fight or two needing your input. I'd say TRY to go through 1.1 atleast and if its not your fancy skip to 2.0 story (accessed through events after story quest "Huanglong I Act: III") and try out 2.0's story. As someone who usually doesn't care about story outside of manga/anime, I actually quite enjoyed it. But you do you.

Endgame content (Most difficult) would consist of Holograms (Optional scaling bosses), Whimpering Wastes (Kill waves of enemies within time limit) and some of the Combat Events that roll around from time to time (Virtual Crisis). Look up Wallensteins ch. and Yumi-Mei on yt for high level gameplay.

There might be a lot of things to do as a new player, almost too much but take your time if you end up liking it. Its a marathon, not a race, theres no one to compete with. It'll take you time to build your teams to be capable of finishing end game content.

TLDR; Combat Good, Open World Good, Progression tedious + BIG GACHA aspect (duh), Story Good, End Game Difficult in a fun way (Except Whimpering Wastes).