"Pay to win" microtransactions, when you can pay to overpower other players aren't successful. The players hate and avoid them, so paying players (whales) have no respect either, so they leave. But the opposite isn't just cosmetic microtransactions. You can buy spaceships in EVE by buying PLEX and spend the ISK on ships. Or on implants to get more skillpoints. You can buy faster XP gain and gold tanks in World of Tanks. You can buy faster XP and IP gains and champions in League of Legends. Yet these games aren't considered "pay to win". What are they then? Let me coin a new term "Pay not to lose". To understand the difference, we must understand winning and losing in an MMO. These games doesn't have a "game over, you lost" screen or a nice endgame cinematics celebrating your victory. There is constant progression in the games, you gain XP, skillpoint, wealth, gear. There can be bumps on the path, minor setbacks when you wipe all raid on a boss or lose a battle. But you grow and grow.
So does everyone else. The speed of growing varies between players. The average or the median defines the "decent player". Not too bad, but not great either. Below him there are is the "n00b". Above him, the "l33t". "Pay to win" games allow you to buy your way to the "l33t" by getting upgrades that matches or outperforms what the best can get. "Pay not to lose" games on the other hand allow you to buy your way out from "n00b" into the "decent".
It's not really hard to get tank XP in World of Tanks to upgrade your tank and don't run around in a weak stock tank. But you can completely skip that by farming XP in a gold tank and converting it. Average players both fly ships they like in EVE and farm for it. Flying a battlecruiser won't make you exceptional. However paying money will save you from the farming part. You lost it? Replace it instantly! Playing with a champion you have is what every League of Legends player do. You want to play with a champion you don't have, no need to farm with your old, buy it instantly!
"Pay to win" means you can't beat a whale. "Pay to not lose" games on the other hand give no such advantage because there is no such thing as "competition for mediocre status". The whale is hiding between the countless average players, flying under the radar.