Plenty of other folks I follow do this kind of thing all the time! You might not necessarily receive engagement from your circle if others aren't invested in the fandom, but it's your journal and you're allowed to derive enjoyment out of journaling. And if you would like folks to put in a little bit of effort and offer some good vibes about your fic ideas, it's really not too much to add a note like "hey, I could use some good vibes" and kind people with spoons to spare will absolutely be like "yo, [this one] sounds great."