Is anyone playing Arknights

Yeah, I've been full F2P for a few years.

Should anyone play this

Probably not lol. A brief review:

Story: I read all of the story up to the end of Chapter 8 (supposedly where it gets good) and was never interested. The adherence to a VN-style format absolutely kills the pacing.

Gameplay: The core game is: mostly okay, but see the Balance section below. They should get rid of energy costs on failure imo, especially of Challenge Modes, because it makes me a lot less likely to experiment. Rating some of the weird variants (none of which cost energy):

-Integrated Strategies: a roguelike where you grow a small stable of operators from randomly-chosen classes and gain powerful relics on the way to a final boss, a new one comes out every year. I preferred IS3 to the new IS4, but it's still pretty enjoyable. Upsides: decent variety, always available (except IS1, RIP) rewards are optional, but broadly useful (a lot of high-rarity materials and XP). Downsides: you need to have a pretty mature roster to stand a chance.

-Stationary Security Service: a (rotating) fixed pack of levels based on rotating operators out to get buffs. Replacing a sniper gives +40 attack speed, for instance, stacking up to 5 times. Upsides: a pretty novel idea and fun to mess around in. Downsides: You need to have a pretty mature roster, some ops skew the mode extremely hard (Gnosis with enough ASPD can perma-freeze, Mudrock with SP regen can spin2win forever), reliant on RNG to get the capstone ops you want to capitalize on the built up buffs when you need them, and the rewards are semi-mandatory for end-game.

-Contingency Contract/Pinch Out Operation/Design of Strife: A challenge mode with a single stage where you select buffs to give the enemy, with the goal of completing runs with specific buff combos unlocked. I usually mess around a bit and then just look up guides when something's too annoying. The high-end challenges are designed to be difficult for whales, so good fucking luck beating them without a squad containing all of Mlynar/Typhon/Surtr/Texalter/Chalter/etc.

-Reclamation Algorithm: A weird base-builder thing with resource extraction. The economy in the last one was too slow to get me to play it (the optimal strategy was to start the first day, get resources, build up your base, and then quit out like 25 times just to get your base going so that it was possible to play the later stages), so I just got the Pallas energy drink skin and then stopped. It's coming back in the future and might be cool, idk.

Economy: Typical gacha FOMO monetization in the form of Limiteds (1 new one per quarter, they'll come back as slightly elevated above base rates in the Limited once a year after that for 3 years, then you have to just buy them for 300 pulls), and what I'm going to call Super Limiteds (collabs that never come back, so far Rainbow 6 Siege (Ash) and Monster Hunter (Yato Alter)). Since starting, I have not missed a single Limited, but I basically don't pull for anything else. The yellow cert shop will eventually let you get just about everyone you'd want, but ops typically only show up there after a year or so.

Balance: is a fuck. There are entire archetypes that are borderline unplayable, and power creep is real (Eyja S2 makes Splash Casters obsolete, compare Texalter with Phantom, Typhon is just Rosa but better). Modern content is usually specifically designed so that certain characters are less viable because otherwise they're too strong (Ifrit, Surtr).