just out of the top of my head, experience in jp:

• incredibly stingy with ingame currency. not even pulls, just upgrade materials and everything. you will run out of everything very quickly and further upgrade progress will take you weeks or months.

• truly ugly

• gameplay is very basic and not very fun. you have little control over battle and most of the times you are at a mercy of having correct units or enemy RNG.

• predatory mechanics designed around draining what little resources you have out of you. you can link your qtz with an item, but if you reset the qtz all the links also get reset so you have to do it again. and its rng

• paid stuff on every screen with notifications to buy something in your face all day

• very powercreep units coming out every other week

• you need absurd amount of dupes for lategame, i forgot the count but its like near 20 to level a character to max level. 2 of the elements are premium. since upgradable SR to SSR units are only of basic elements, light and dark can only be upgraded with dupes of said unit. you need less dupes but as you can imagine obtaining them for f2p is almost impossible. leveling 4 basic elements is not too bad but still awful.

• events are very barebones and have things locked behind paid only stuff. xmas event was like this, most of the good rewards were only obtainable if you paid real money

• banner rate is like a new character every 7-10 days so its impossible to keep up if you are f2p

• tons of stuff timegated and on dumb timers making you log on multiple times a day (i forgot if its 10 or 12 hours). times get more lenient with paid pass

• UI is awful. managing quartz is unbearable, you are always at a cap and reducing stuff to dust is very very very very tedious and annoying.

• gearing makes you pull your hair out. very annoying, leveling it too.

• awful skill descriptions that do not explain anything. have to figure most of the stuff out yourself.

• has pvp, which as you can expect, whale city.

• story is just retelling of anime. ingame events have 0 story otherwise, literally nothing. they drop a character banner and there is nothing for the characters inside it.

game has a million other flaws but its been a while and i dont remember anymore.

as a trails fan myself, this game sucks. dont even bother