I am not sure what the issue is here? Treklit has had several gay characters and relationships in it hasnt it?
Absolutely it has. But the existence or otherwise of those relationships is not really the OP's question. It was more that those relationships didn't seem to be happy and long-lived ones, but were always confronted with some trauma of some kind.
And the thread has demonstrated that while there may be some truth to that, there are a number of reasons why it might have come to be, both within and without the narrative, and also that there was no malicious intent behind it. Doesn't mean there might not be room for improvement, of course, but then there always is.