I think that a lot of depends from the game, its promotion and liquidity of the game.
To be popular Play2earn game must have a good liquidity, big ecosystem and a lot of users.
In such case gamers will be able to earn money.
If game has a big community and a lot of players it is more simple to sell in-game NFTs inside ecosystem of the project.
Very often NFT is possible to buy and sell only on the platforms marketplace. They do not sell NFT on other marketplaces.
That is why the liquidity of the ingame NFTs are not very high.