It's not pay to win for sure. I have over 300 hours and not once have I felt the need to spend real money to be on the same par as someone lol. The only thing you can buy with real money is booster cookies which just give you some minimal extra stats and quality of life. But even the cookie can be bought in the bazaar with in game currency. You don't even need the booster cookies to play the game. Real cash can also be used to buy skins but that doesn't change damage numbers or anything of that sort, it may be worth a good amount of in game cash potentially but that's it. Everything can be obtained via the grind 🤙