Hi! I use a fountain pen all the time. I learned to use one as an exchange student: at my school in Belgium, all work needed to be completed in fountain pen (this was in 1996, which i just now realize is almost 30 years ago).
i hate talking on the phone and i zoom all day at work, so i recently decided to start sending longhand letters to my old friends and distant family. I’ve had pretty good response, though a few people seemed puzzled.
I write essays and short fiction, and writing on paper is just better for me. On a word processor, i tinker with wording too much: one sentence can take me ten minutes to finish. On paper, i move on and fix things when i type it up later. I think paper lets me build momentum.