TBH I don't see any power creep - the best event girls were the early ones, which are now on general release, some of the best 5* were on release/early....if anything power has decreeped
As there is no real 'win' there can be no P2W, it's pay 2 waifu or support the game
...possibly as content comes out newer players may have the 'need to grind a little' moments where we've been keeping pace....so then pay to skip grind becomes a thing...
At no point did I say this game is "pay 2 win"; in fact I said the opposite. I only mentioned it to illustrate that while the gacha is a money-making mechanic for the devs, the ability to use it (in the form of FGs) doesn't leave F2P players in the cold (thereby denying any "pay 2 win" claims).
If the only way you could ever get 5-6 star girls was by spending Nutaku gold, then the argument would be very different. That isn't the case here.