This is not the definition of pay2win. There are almost literally zero games where there is an item in the game that grants power, that can *only* be achieved through a real-money-transaction (RMT). That would be stupid, and nobody would play it. The whole reason the free2play model works is because buying items with RMT doesn't usually feel too unbalanced for non-playing players. PC Gamer wrote a great article about this, contrasting good microtransaction games (League of Legends, Planetside 2, etc.) from the ones that functionally become pay2win (ArcheAge, etc.). Instead of asking, "Are there items that can EXCLUSIVELY be purchased with cash?" in order to define pay2win, instead we need to ask a more nuanced question: "Is the grind for free2play players reasonable, such that free players can still reasonably maintain competitiveness, without having to pay to keep up with the power advantage?" If a free player doesn't stand a chance in hell competing against paid players, then it's pay2win -- regardless of whether the free player can still "TECHNICALLY" achieve items without paying (if they grind for a year straight, etc.).
These sentiments are where a game can start to flirt more with a functional definition of pay2win. If the grind in a game is so egregious, and the real-money-transactions are so important and necessary that you almost can't even imagine playing the game without having them, then it starts to become more pay2win.
All this being said, I'm not saying MWO is pay2win -- because I've never played it, and I have no idea. But based on your statements, I can't say that I trust your assessment of the game being "not pay2win" given what your definition of "pay2win" is. It's not a question of whether you can buy power that's unachievable by other players, it's a question of what "achievable" really looks like. Just because a player can "technically" get something, doesn't mean they can functionally.