A truly decentralized crypto game is a smart contract where the outcome of a transaction is unknown to both parties until they agree to it. For example, "crypto roulette": an Etherium smart contract where N parties enter M coins, and then a (pseudo-)random-number generator decides which party gets the spoils.
You could build off this concept with other games like "crypto blackjack", "crypto poker", etc. where you somehow enable user input and output once players enter their coins (this would need a timer, so if a player doesn't input in X time they are disqualified. I really doubt this is currently possible and I don't even know if it's possible at all). You could also use NFTs instead of coins, and replace the basic random-number generator with a more complex algorithm which simulates a kind of "battle" based on parts of the NFT hash. Kind of like a battle between Axies.
But the fundamental point is, the entire game is a smart contract. There is no centralized server handling the transactions, and the game-maker can't "shut down" the game or change the rules or create an overpowered NFT. And the rules are visible to anyone (you can still add "cheats" but you have to hide them, because other players can find and use them too).
I'm not advocating for Axie Infinity, but I think there are multiple sides to this.
The bottom already fell out of Smooth Love Token.[2] The Axie Infinity governance Token is down a bit after a big runup.[3]
"Daily Earnings of Typical Axie Infinity Player Fall Below the Philippines’ Minimum Wage Line".[1]
[1] https://block2block.io/daily-earnings-of-typical-axie-infini...
[2] https://coinmarketcap.com/currencies/smooth-love-potion/
Huh? Axie Infinity is a Ponzi scheme. They're the people behind the Smooth Love Potion token. See chart for that.[1] They prey on poor people in the Philippines and Vietnam with a pay to play game that costs about US$1000 to enter.
[1] https://coinmarketcap.com/currencies/smooth-love-potion/