Genuinely, I understand why we've ended up in this place when it comes to describing/recommending queer media - for so long, there was so little of it that, when it came to word of mouth, the presence of queerness was itself the primary basis of recommendation. If the work also happened to be good, then so much the better, but the baseline, redacted-for-ease-of-transmission signal boost was simply This Is Gay. And when there wasn't much on offer, that worked! We were desperately trying, not just to see ourselves in stories, but to prove that there was a market for more - that queer audiences would show up for queer content, even if the genre was outside our usual bailiwick.
But the more queer works are published, the less useful this rubric becomes - and to further complicate matters, the rise of trope-centered marketing for romance in general and queer romance in particular, which often borrows terminology common to tags on AO3, has trained readers and creatives alike to frame stories predominantly through the lens of character dynamics. Which, to be clear: there's nothing wrong with this in and of itself! If you want to either give or solicit recommendations based on, say, grumpy x sunshine but make it gay, I'm not about to harsh your vibe. And particularly when it comes to romance, where the character dynamics necessarily constitute the backbone of the story, it often makes sense to do so.
But there's a very salient difference between romance as genre (where the romance is the story) and romance as device (where the story contains romance) which, particularly when it comes to queer books, is frequently erased by these conventions - which results, as OP rightly points out, in queer stories with other loadbearing themes, philosophies and plots being, if not technically misrepresented, then certainly undersold in terms of all that they're doing.
The Locked Tomb series, for instance, is, indeed, about gay necromancers. It's also a purposefully anachronistic science fantasy mindfuck that plays explosively with humour, voice and genre from book to book while still remaining, in essence, a sequence of locked room mysteries. By which I mean:
Gideon the Ninth is a locked room mystery where the room is God's laboratory and the mystery is what the fuck he was doing down there; Harrow the Ninth is a locked room mystery where the room is the narrator's body (and also, at times, the space station she's inhabiting) and the mystery is how she ended up that way; and Alecto the Ninth is a locked room mystery where the room is the personality that forms in the absence of memory and the mystery is God's secret past, with the necessary caveat that God here is not meant figuratively, but in fact refers to a literal, actual, walking, talking character who is also just Some Guy. It's about the intransigent nature of bodies, the fuckiness of personhood, the eternally compounding sin of pride, niche millennial humour and the gothic, philosophical splendour of toxic lesbianism (in space). It's got a lot going on!
And, sure: it's shorter and simpler to sell it as just gay necromancers, to say nothing of the fact that this description will still hook a lot of people. It's not inaccurate; it just presumes that this is the most important thing anyone could want to know about the book, and that won't always be so!
Look at it this way: if you're already shopping in the LGBTQ section of the bookstore and ask an employee for a recommendation, and they pick something off the shelf and tell you, "Buy this, it has two boys kissing!", that's vastly less helpful in context than if you'd walked into a store without an LGBTQ section and asked for a gay book rec. You see what I'm saying? It's a scarcity mindset that we've carried over into (comparative) abundance, and it's no longer serving us well. Gay is not a plot or a genre by itself; it's a component to be explored through the lens of plot and genre - which means that, in order to talk about one, it's also worth discussing the others.
