I think that's true. The 1780 stuff can usually be dismissed as being something that no-one seriously believes any more. The 1980 one can't.

It's not just the cultural stuff, though. I read Dream Park and the Barsoon Project when I was a kid. Loved them to bits. Recently I found a copy of The Voodoo Game in a second hand book store and finally finished the trilogy. Don't get me wrong, I enjoyed it, but it was like watching an original series BSG episode and expecting it to be as good as... modern BSG.

I remember after reading Ringworld on a friend's recommendation, saying that it had one too many alien species with non-sentient females for me. One, okay, interesting idea I guess, two, now you're doing a thing.

Ringworld: Adventurer Louis Wu visits the titular megastructure along with three amazing aliens - Nessus, the two-headed Puppeteer, Speaker-to-Animals, the felinoid Kzin, and Teela Brown, the Wo-Man.

For the Puppeteers, both the sperm and egg producing sexes are sapient, it's their surrogates (a different species) that are non-sapient. Doesn't seem much different to humans hypothetically developing artificial wombs and losing much of our sexual dimorphism over time. If humans gestate their young in non-sapient artificial wombs in the future, would that make us sexist?

Well, except they explicitly call the non-sentient ones female (also stupid, and property), and the sentient ones are both referred to as male.

Well that's a semantics issue. Niven might argue that since the egg-producers don't gestate the young they're fulfilling a "male" role of merely producing gametes. But I'd argue that the female role is defined more by producing egg cells than by gestation: female fish produce eggs but don't gestate their young, and we still call them female. Therefore the "male" puppeteers that produce eggs are still truly "female".

The sentient ones are famously docile, cowardly and manipulative. I don't think calling them female would've been striking a great blow for progressive literature.