Play money or free-rolls, they both have a low standard of play because players use them for practice, you will always get the idiots pushing all in with any 2 cards simply because it has cost them nothing to play, but if you wait until the dust settles you then get to play poker.
I have and still do play with play money when I want to learn a new format of poker like "Razz" or "Short deck", still not very good in either, so I certainly would not use my
bankroll to practice them.
It gives you a solid grounding in the way the games play and of course cost's nothing to learn the basics, but in all forms of poker the only way to really learn is to lose a few times and improve your play.
When the fun Stops, STOP!