It really wouldn't matter whether or not Conor cared about his legacy- in order to have one, you have to beat top fighters, which he has shown he cannot do except at the lower weight class. In other words, you must have the ability to actually have a legacy before the idea of caring about it even becomes relevant.
Conor will be remembered as increasing fight popularity for a brief period of time due to his ability to get attention through smack talk and hooliganism. If you want to call that a legacy, so be it.
Rousey actually will have a bigger legacy, because even though she won't be remembered as a great fighter perfprmance-wise, she smacked talked, beat the lesser fighters of the time, and in doing so, popularized WMMA to the masses. Conor can't really say anything like that.