Happily, this is one of those problems that is very easy to fix. All it needs is people who like diversity drawing and writing it. Just make it a habit that when you design a new species, you include some diversity. There are all kinds of things you could choose -- different colors, genders, cultural practices, religions, mentalities, body shapes, and so on. Aim to represent at least two characters with divergent traits when you introduce a new species. That not only cuts down on monotyping, it helps distinguish them as individuals.
Here are a few of my examples ...
An Army of One: The Autistic Secession in Space has a huge range of neurodiversity. They're all human, but not the kind that most humans write about.
A Conflagration of Dragons is a series where I made up six new vaguely humanoid species -- the Six Races -- plus the dragons, who are also sapient but nobody counts them among the Six so there are technically seven. Each of the humanoid races correlates to two of the four elements (Earth, Air, Fire, Water) and that influences the traits they have. I have posted details about the Madhusudana, Shu, and Beneberak. The dragons are all one species, although they have different color phases (red, blue/green, bronze, black) depending on which elements they favor. You can see a great deal of color variation in this series.
Feathered Nests features an alien species who resemble birds. The males have three genders -- aleph, beth, faeder -- distinguished by both physical and psychological traits. The females have two -- modor and gimel -- distinguished by sexual orientation rather than physique.
Frankenstein's Family has werewolves with at least two subraces: there are werewolves with light-skinned and dark-skinned human forms.