You're conflating two very different types of progression here. Have you played many roguelikes before? Generally, the kind of unlockables which persist between runs are intended to increase the number of options a player has rather than raw power.
In terms of general difficulty outside of Endless Mode - it's useful to know that players are having difficulty with Noriko. She's pretty easy to beat in my testing once you understand the mechanics, but given that she's the first available prey scene and you're far from the only person having trouble here, I'll think about how that scene might be toned down a bit.