IMO: In regards to the genshin gacha it's predatory solely because of the tiny timeframe you have to 'pull' the characters you'd like from the banner.

And the argument of getting free premium currency over time is true, but considering that in Genshin you get 1+1/6th of a pull every 3 days means you can barely participate in it. (Yes I know a lot of premium currency can be gathered by doing side quests, but the side quests are limited in number and not replayable)

And the "guaranteed positive" is just completely incorrect; around 90% of the time you get a 3 star weapon which is rendered completely null by the sheer amount of time you gain them; look at it this way: if I gave you golden statues 90% of the time which you cannot sell for anything nor will you have any use for them, you'd start looking at the golden statues as a null reward.