what we now conceive of as 'zombie', including the word, is a modern idea not based on historical predecesors.
So actually you don't like your conception of the idea of Undead. You're not allowing for originality - if the Undead were to be included, do you really think that they'd just have zombies? Despite the name Undead (and zombies) usually referring to generic conceptions, its and umbrella term encompassing significantly varying ideas. It's up to personal preference really whether you like them or not, in which you shouldn't dictate that people who want them should be denied. I don't like Dwarves, and not just for aesthetics. Does that mean I'm telling DoF to steer clear? Of course not.
And how are they different genres?