Most games—the majority of free MMO games—are pay 2 win sadly. From the top of my mind, DOTA 2 is currently a free, play 2 win MMO that I played some time ago. You only need to pay for the cosmetic stuff. But then there is DOTA plus. But honestly, even the paid games are turning into pay 2 win these days with all that shortcut kits and other loot box craps. It’s a sad state of gaming today. So to answer your question, there are no online games these days that would qualify as a truly skill based play to win!
