Strongly disagree. Being gay here has no significant to the story. She contributed to society by protecting those who wanted to reproduce as long as she's still capable. What's the point of having so much babies if everyone are busy making them without anyone to do all the scouting and resource gathering.
For as long as she is able - that won’t be forever. There’s no social security, welfare or medical services in the TLOU world. When she is too unfit (as a result of injuries and poor nutrition) or simply too old to be useful, she becomes a consumer of resources and has not contributed children to her and the community’s future upkeep.
That’s what children are in “frontier” civilisations - insurance and investment for the future. Note how in our time the poorest countries have some of the highest birth rates and also the lowest welfare and support systems.
As for the scouting and resource gathering - that’s what men are for. They don’t suffer the debilitating physical effects of child bearing. A voluntarily infertile female is not as useful as a fertile one in that post-apocalyptic society. Ellie isn’t as useful as a male and she isn’t as useful as a child bearing woman if she chooses not to conceive.
Ellie is literally another mouth to feed who is less valueable than the others. She even says as much to Joel when she tells him he should have let the firefly doctor have her so her life would have meant something.
The murderous revenge rampage is Ellie coming to terms with her own uselessness in a world that needs people who can build. She can only destroy.
Beyond that though, human history shows that homosexuality isn’t necessarily an impediment to child birth - the Greeks and Romans were quite liberal about it, the women had children and female lovers if they wanted as did the men.
TLOU though takes our current sensibilities about sexual orientation and transports them to an apocalyptic scenario - a scenario where modern views of sexual orientation would lead to the downfall of the community. Dina is a somewhat more realistic character - she got pregnant and she also preferred to live a lesbian lifestyle.
Even that is an unrealistic outcome though - having dropped baby one, she would be trying to conceive the next one pretty quick so the “idyllic” lesbian relationship shown towards the end is a bit silly. I imagine when Ellie finally finds Dina and baby gone at the end, Dina is back with a guy somewhere and possibly pregnant again. In that world you’d need to conceive probably 5 or 6 children to have a decent chance of 2 of them surviving into their 20s and up.
Ellie isn’t useful in that society and at the end of the game she sets out by herself - she recognises her own uselessness to the community.
Oh, and Ellie will die too. She’ll die alone and childless judging by the story arc. Joel’s mistakes - not sacrificing her in TLOU 1 and then raising her to be a lesbian - will potentially be the downfall of humanity. He screwed up not once but twice.