IMO the "problem" is that RH doesn't tell you that (or at least their marketing makes it confusing at minimum). The way they describe it as an "instant bank transfer", not "we give you margin until your transfer clears". The former gives you the impression that its your money that you're trading with, while the reality is it's a margin account.

That's why a lot of people were angry. They were forced to sell GME because they were technically using margin and it got called, but they thought it was their own money from their own bank account. The optics are that RH forced them to sell GME when they didn't want to.

If you do any trading at all, you want a margin account so you don't have to wait for settling before making another purchase. While technically the money is borrowed for the 2 days to make your trade, I would never considered it borrowed in the typical use of the word margin.