The free-to-play games I've enjoyed tend to have a reasonably priced package with permanent rewards. So if you like the free content, which in bygone days we would call a "demo", you can unlock the rest of the game for a one time $20-$40 fee, formerly known as "purchasing the game".
Most F2P games are actually way more generous with demo content than in the old days, though for the multiplayer ones that's understandable since the free players can be useful for keeping the player count high enough.
Microtransactions are a different issue, but I don't really mind them. I bought fancy weapon skins for Killing Floor because I was grateful to the developers for their continued efforts. Whereas I'd never buy a TF2 hat (mostly because I seldom play) but the sale of crate keys to impulse buyers allows Valve to offer us the game for free.
And when microtransactions give significant bonuses, there's no shame in losing to some cow who spent a lot. And if it gets frustrating, you can walk away - everyone else probably is. So generally games only try that stuff when they're already crappy, or if they have massive balls (like Diablo 3, which I think mostly downplayed the real-money auction thing after launch).