Ampies are farmable normally and aren't even in short supply, not to mention that buying ampies here is a complete ripoff.
In time, everyone will have a few maxed out units. Ffs, even DMM players have the luxury to max out several GRASS units, and they don't have our "buy ampies with FG" model.
This is all beside the point as feeding ampies only serves to boost your max TP, which in the long run means nothing except bragging rights. When everything in the game is clearable without spending a dime and there's no real competition to speak of, it is by definition NOT P2W.
That's like saying KanColle is P2W because paying players can marry multiple shipwaifus, even though it's hardly necessary for the content of the game.
What part of "pay to waifu", not "pay to win" was not clear?
You said it yourself. All players will get the FGs to max their slots or refill their stamina in due time. Paying players have the luxury to gamble their FGs, which does nothing except leave it to RNG and end up getting nothing but bronzes and silvers 90% of the time anyway.
Because in the end, FKG has shit gacha rates that we all tolerate because they provide plenty of free stuff elsewhere. Any gacha waifus we want, we leave to luck or shell out money for the guaranteed sales. And that does nothing as far as actually *winning*, because gold gacha girls don't completely outpace event girls and rainbow girls are complete overkill for the content of the game.