Pay to win is a consistent advantage where the only means of catching someone willing to spend hundreds of dollars is by matching their expenditures because you'll never catch up through grinding. For example, in Black Desert, world bosses drop loot based on DPS totals and have multiple built in OHKO mechanics. Should you die, you will not only be forced back to the closest city or town, but lose 1% of your EXP and have to run all the way back-- inevitably losing out on the loot ranking. Except! You can buy Eilon's Tears. This instantly revives you wherever you died and removes the EXP penalty. Therefore, you can jump right back on the boss. Due to their cheap attacks, the zerg-like "strategy" encouraged and their massive HP pool, the most efficient, and in some cases necessary, way to obtain loot is by having stacks of Eilon's Tears, otherwise you'll never come close to people who do.
That, is pay to win. You have no control over progression and the most optimal solution is to spend money.
Compare this to FFXIV. While someone may be able to participate in Savage faster, they gain no consistent advantage. And, that advantage is limited only against brand new players who opt out of skipping content. These potion skippers gain absolutely nothing by spending money on anyone who will have reached Heavensward up to 3.55 by the time of Stormblood's launch. Furthermore, if Square does bundle a free potion with the expansion, it's entirely by choice whether you want to go through the long way or skip ahead. No cost involved.