Well actually...
AoS absolutely featured a character that could have been a Mutant, and he even shared a codename with a character that was a Mutant in the comics, Scorch. His powers were never made 100% clear (they left it open that he may have simply been that way genetically, and in fact his genetics were used to perfect the Centipede formula), and he was on the show way before the Inhuman stuff. He probably wasn't an Inhuman. It was also established that S.H.I.E.L.D. was keeping various "gifted" under surveillance/arrest (for the villains) in the first season, and presumably none of them were Inhumans. They didn't even know about them. Friggin' Man-Thing and Griffin exist in the MCU according to AoS.
AoS absolutely featured a character that could have been a Mutant, and he even shared a codename with a character that was a Mutant in the comics, Scorch. His powers were never made 100% clear (they left it open that he may have simply been that way genetically, and in fact his genetics were used to perfect the Centipede formula), and he was on the show way before the Inhuman stuff. He probably wasn't an Inhuman. It was also established that S.H.I.E.L.D. was keeping various "gifted" under surveillance/arrest (for the villains) in the first season, and presumably none of them were Inhumans. They didn't even know about them. Friggin' Man-Thing and Griffin exist in the MCU according to AoS.