It does. Understandably we creatively base things on our knowledge and perception of how things work, so we've always had the dual genders in every iteration of every alien (even the one gendered species in that TNG episode were historically male/female). It makes sense in a lot of ways to go beyond our knowledge and try and showcase something radically different from the 'norm'.
I'm not sure how having four sexes of Andorians would make them die out though. If that was made a canonical thing and there are four sexes, and there always were four sexes, surely it'd be sustainable otherwise they'd have died out long before they got into space :/
Variety is good. Even ham-fisted plausibility is better. Such a species wouldn't likely evolve in the first place, to say nothing of surviving long enough to reach "civilization", to say nothing of appearing on the Kardashev scale, leaving its own planet, much less colonizing other worlds.
It's similar to the Klingon scientist problem, only instead of it being a question of Klingon society somehow producing scientists, it's a question of a four-gendered species actually evolving in the first place and being able to reproduce sufficiently. Nature and evolution are lazy. If I can anthropomorphize a bit. Like water finding the path of least resistance. There's dozens or hundreds of other methods of reproduction that are simpler, easier, and involve less chance and work than four genders. Note this isn't about non-binary genders and identity or any of that, rather an actual biological requirement of four members of a species to create one new one. In our knowledge of life on Earth, limited though it is, that's basically unknown.
Just take a second and think about it. In humans, we have roughly a 1:1 ratio of births between the two dominant genders (male female). But you need one each of the dominant genders to breed one child. So to replace each parent, you need two children (hopefully one of each gender) to survive to sexual maturity and successfully breed, which is why until recently women had so many kids, because many of them would die before reaching either of those markers. Or the mothers themselves would die in childbirth. But this scheme is basically doubling that, doubling the risks, and doubling that chances of failure. Instead of 2 parents with complimentary genders, personalities, and fully functioning bits, you need 4. Instead of two children living to sexual maturity and successfully breeding, you need 4, and you'd better hope you're pumping out all four genders or some other family is over producing what you're not. Any significant dip in the ratio of births would result in something like the ENT episode Cogenitor. Which is a great follow through with the notion of multiple biological genders, and a great allegory for the notion of gender roles in America up till the late '50s.
Yeah, I know. It's just a show. A cheesy, silly one at that. But one of the things I love about SF is reading and watching creative types honestly work through the what ifs. Assume something is different then working logically through the consequences of that difference. The four-gendered Andorians fails miserably at the "working logically through the consequences" phase.
Didn't the Denobulans have several sexes? I recall a few (cringeworthy) snippets from Phlox to such effect.
I agree that it seems silly; because humans have only 2 "primary" sexes (not speaking to gender identity) and it makes it harder to relate, but if it can be used to explore human issues of sex and gender without getting political, why not?
I'm all for exploring human issues of sex and gender. I'm even fine with it getting political. But it's still got to make some basic sense on a biological level. As above, even a ham-fisted attempt at logically following through with the consequences is a basic requirement for me.