Oh Creators above, I promised myself I'd never join another of these conversations again...
It's really not tbh.
First point, if he fell for a dalish when they're not his people by his own words, he can do so for a human as well. (not saying I want it, as this point for me is about racial gating in general, which brings me to)
[snip]
I'm afraid I have to disagree with you there. It's true that Solas doesn't consider the Dalish "his people," but he still seems to feel some affinity for the People. More specifically, People who he feels are spiritually connected to what it means to be truly elven. Specifically, elves from his time. He often shows reverence for ancient elven history, architecture, magic, etc. (Though he doesn't romanticize or idealize them, and calls out anyone who does.) I feel it's implied that part of his frustration with modern elves (both city and Dalish) is their complete disconnect for what he feels it means to be elven. He seems to remember with pain and fondness the days when "everything sang the same" (as Cole puts it), when elves "lived at a pace that sustained us for ages," when immortality and magic were a byproduct of "just being elven."
He often badgers Sera about her elfiness, trying to get her to feel some feelings of kinship or affinity for the elven people, language, culture, magic, the Fade, etc. If Sera romances a female Lavellan, he remarks that "it is natural to desire another elf." If you go back to the elven cultist whose father asked you to tell him to prepare a potion for his mother's lungs, and let Solas speak to him, he rips into him, saying, "You have the pointed ears of our people, but not the spirit." Solas seems to feel that most elves at least have the potential to embody the spirit of what he feels it means to be elven, even if they don't automatically get it just for being born with pointed ears.
Now, when you gain enough of Solas' respect, he says, "You show a wisdom I have not seen since... since my deepest journeys into the Fade." Who wants to bet he was going to say, "Since before the fall of Arlathan"? He clearly misses that time, and feels reverence for how elves used to be (if random comments like "My people built this" are any indication). During the romance, he specifically has to say this before the Romance will take effect.
That's something a human could never share in any more than a dwarf or Qunari.
He might not feel a female Lavellan is "his people" for being Dalish, but he might feel it because she's an elf who has reconnected with the ancient ways, spirit, virtues, and values (wisdom, subtly in her actions, understanding of the world).
Does that make sense?
It's fine that he's gated, same as it's fine that he isn't gay. I'm just saying the argument that it allows for more is incorrect.
Actually, this seems to contradict what you said above. By your logic: if he doesn't feel the Dalish are his people but romances one anyway, then that means he should be just as open to a human. Logically, one would assume that that means he would be just as open to a dwarf or Qunari (or at least a Qunari, since dwarves don't dream--then again, a dwarf who showed just as much enthusiasm to learn about history, magic, and the Fade like Dagna might impress him...). Yet, you say the same logic that would lead one to think the lack of kinship for Dalish that allows for him to romance a human doesn't leave one open to think he should also be open to romance other races?