Very true, in games like spyro, sometimes dubbed "collect-a-t(h)on" i never had any problem with them, i actually quite liked them but probably very well thought out rewards systems, as you say, are a big part of that.
i would say it is, it probably wont take you that long to skip till the new content (its boring to do , but it doesnt really take long on non grindy games)
All this.
Also , i know a good chunk of people do like them, and they should get some, but i bet most people that read erotic VNs are not getting into it to see monstrously huge dicks.
I dont 100% hate grinding (FE: Love MH like that lasat commenter), but the types of grinding i ve encountered in erotic VNs feel mostly like low effort padding, designed to artificially inflate the playtime.