Absolutely. I write some pairs that I know very few people will read or care about, but I still write it because it makes me (and maybe one or two other people) happy. I write fics sometimes just for me that I end up not posting at all.
If writing makes you happy, do it. It doesn’t matter fuckall what other people think. It doesn’t matter if one person or 5 or 10,000 people read it. Write because you want to. Write what you want to write because you want to.
I know sometimes it can be discouraging to think no one is reading what you put out there, but people will come. And you’l find those that support you through it. Heck if you need to, my ask is always open.
I strongly support writing, any writing. Don’t let anyone tell you that what you write is worth less then anyone else’s just because it’s fanfiction, or something they aren’t interested in. Write it anyway.