If this was a dragon quest or standard fantasy slime I'd be OK with this. But this slime walks talks and looks like he has a family waiting for him back home. Dude probably has a name you've completely ignored. Stand up for Slime Rights!
The more he talks about trying to "rule his past world" and "not understanding humans" really makes me question if he really was the "demon lord" in his last life, just called a different title