I'd say this is half true depending on how long you play for (assuming you're just playing casually and not putting any money down). This game's formula is pretty much the same as many F2P games. It's enjoyable to a certain point/level, then you're stuck and can't advance because those who paid for the cash bonuses simply have too much of an advantage. And in a game like this, it is definitely pay-to-win.
I know there's people in the top rankings without a SM, but the only way they'd make up for that is to have really good talents. And of course, the only reliable way to get good talents is to put money down.
So I'd say to OP: take your time, enjoy the game now while you can before you hit that glass ceiling.
I don't agree that this game is strictly pay to win. You can win with time as well. Put in the time and you can do very well.
Doing very well and winning are two different things. I'm not making up 20 levels in the arena with good talents because I spent time leveling them. I rolled for them. Want to be in the top 10 in the Arena? I don't ever see it happening again without a spirit mage and good talents as well as leveling.
Just my opinion after seeing the competition inside the top 25. Good luck and well done to a couple of you without a mage in the top 50. However, they all had amazing talents to make up for it.
It is pay to win, and grind to compete. Just my honest opinion on this game.