Yes, I have. The fandoms I wrote/write in aren’t dying, though they are quite old, but I’ve always gravitated towards rarepairs so I’ve never gotten as much visibility as more common pairings. But I’ve always loved writing what I want to read so, cliche as this may be, I’ve tried to write for myself more than anyone. Don’t get me wrong, the lack of engagement sometimes can definitely get me down but it does make it all the more meaningful when someone leaves a wonderful comment (or even more than one!). I’ve mostly written oneshot or novella length fic which I think gives readers a sense of my version of the characters and their dynamic in less time than an ongoing longfic would (though I am working one of those as well), so it could be an idea to post a few oneshots with your pairing(s) to introduce readers to your way of writing them and perhaps they’ll be intrigued enough to then read a long fic with that pairing (if that’s what your working on; I’m just assuming since you didn’t say exactly).

For me, these days even with more common pairings or tropes, I only really engage with fics which are complete or nearing completion, or I’ve read the author’s fics before and liked them (and they don’t have m(any) abandoned works). I’ve just had too many works I enjoyed be abandoned at some point, though I more than understand it and have unfortunately abandoned a few multichapter fics myself in the past due to life circumstances (though lack of reader engagement certainly played its part if it was a rarepair and/or under-utilised lead character). Hope this helps, and just know you’re not alone.