[@Monochromatic]
Hey, thanks for sharing interest. Basically, any major feature of the three races (such as flying for griffins, magic for djinns and strength for humans) is diminished with half-breeds to the point they could hardly be used in combat. For example, a griffin-human crossbreed would have atrophied wings that would only let them glide for short distances, even less if they've built up any muscle, and their only weather-manipulation ability would be to walk on clouds. Djinn-humans would still have the basic telekinesis magic, but their specialized magic would be only for mundane use: a fire-magic specialist could only put on a campfire or cook, a healing-magic user could disinfect wounds but not actually close them, etc. And while they would have arms, they would be stubby ones like a T-Rex would have.

There's also the fact that in the setting, half-breeds would be considered vile abominations, and are shunned by society.