P2W discussions always just function if you have two people that have the exact same basics. So they have both the same time to craft stuff, the same material and the same amount. Now as soon as the amount is over the limit of the two retainer the other will have the advantage with their paid one. You need to use two similiar people otherwise ypou cant really argue about a "win".
I mean you can have a booster and person A buys it. If person A barely does any DPS than that one would still lose against person B that still is better without it. But if both of them are the same then A has suddenly quite the advantage over B thanks to paid money.
P2W is not always just about something that gives others no chance. Its about making it easier. For example someone that has more Gil thanks to more retainers will get stuff way faster in the same amount of time that someone with only two retainers has. Saving time is the win in that example.
P2W never completely hinders the other one to finish the content. If you sell a booster or gear with certain stats would probably count as P2W for most. Yet nobody necessary wins anything with that too. People could still clear the content. If you argue it like that nothing is ever truly P2W. Because it never stops someone from doing content without it. It just gives them an advantage.