I'm not a fan on in-game currencies because it masks the proper value of things. Microsoft got in trouble doing this on the Xbox 360 when things cost an arbitrary amount of 'Microsoft Points'. They ended up putting proper currency valuations on things instead.

I don't mind in-game purchases. Epic know that parents play Fortnite as much as kids do and are happy to put in skins like Robocop and Sarah Conner which go way over the heads of a junior audience and also pull money from my wallet!

Everything else, from loot box mechanics to paying to avoid an artificial grind is just outright predatory. This is why people still love Nintendo I suppose: they know the inherent value of a good piece of software and don't need to resort to F2P mechanics because the developers built a crappy game.