I actually want to get bogged down to semantics, because it is pretty relevant in this context. What you actually understand biological essentialism mean if we apply it to actual different species?
I’ve given you my definition twice now. Tack “oid” onto the end of “human” in that definition and it applies to D&D races just fine.
Biological essentialism is generally used synonymously than biological determinism: that something is due biology rather than other factors. I.e. nature part of 'nature vs. nurture.'
Biological determinism and biological essentialism are very closely related concepts, but they are not interchangeable. Biological
essentialism is treating someone’s
essential qualities as biologically determined. How strong someone is is absolutely biologically determined. Whether they are “a jock” is not, and treating it as such is called “biological essentialism.”
No. There was 'or' there.
Gotcha, my mistake.
Perhaps you should be a bit less sure that you can accurately determine what is and isn't problematic?
I’m not sure that I can in all cases, and it’s those cases I would like to actually discuss, instead of wasting time and energy bickering about things that are obviously not. Can we please put the stupid examples like aarakocra flight and dragonborn breath to bed so we can talk about the cases with actual ambiguity like Goliath strength and gnome intelligence? Thanks.
I mean, it is not like that, but it is also not exactly completely unlike that: "A changeling can shift its face and form with a thought. Many changelings use this gift as a form of artistic and emotional expression, but it is an invaluable tool for grifters, spies and others who wish to deceive. This leads many people to treat known changelings with fear and suspicion." Then it also goes to tell how they often live among other species without their knowledge.
Nothing in that quote ascribes essential qualities of changeling nature to their shape shifting. “many changelings use this gift as a form of artistic and emotional expression,” not “changelings are artistically and emotionally expressive thanks to this gift.” “It is an invaluable tool for grifters, spies, and others who wish to deceive,” not “changelings are grifters and spies who use this tool to deceive.” “This leads many people to treat Changelings with fear and suspicion,” not “Changelings should be treated with fear and suspicion.”
That is result of their essential biological nature...
No, it’s a result of their biology. Extrapolating to their essential nature, such as calling them “natural athletes” or what have you
due to that biology is what we call biological essentialism.
Whilst I understand the desire to have all lineages to be equally good for every class, D&D classes are not relevant to social justice, they're arbitrary made up categories for game play purposes. It is not any more essentialising to be good fighter than a good weightlifter just because former happens to be a class in D&D and latter doesn't.
It is essentializing for an entire race of people to be better fighters than entire other races, just as it would be for an entire race of people to be better weightlifters than entire other races.
Reasonable by whose standards?
The general D&D playing public?
Ultimately we cannot just evaluate these things based on our gut feeling. It might give some indication, but it is far too subjective and we're blind to our own biases and privileges. There should be at least some sort of logically-semi-coherent framework.
We are working with a logically semi-coherent framework, it just isn’t completely deterministic. It requires socially constructed consensus, just as all such frameworks do. But pointing out absurd examples that are obviously outside that framework and trying to claim the framework is useless because it doesn’t deterministically rule them out does not help to build that consensus. It only distracts from the process of building that consensus, which is why it comes across as bad-faith to do.
Superficially. If that's all your fantasy species has going for them, I wouldn't bother.
Ok, then you don’t have to bother. The rest of us will enjoy our cool game with imaginary people who look different and have different capabilities than humans but aren’t treated as monoliths because of their different appearances and capabilities.
And then you cannot describe different species! They cannot be mentally different. Saying "some dwarves are like this, but then again, so are also some orcs and some humans" is useless.

That is the problem.
It’s not useless at all! On the contrary, it opens up room for more varied stories to be told using them, and makes them infinitely more nuanced and interesting characters.