Earlier quoted context omitted.
I recently started journaling by hand and was somewhat frustrated with the excruciatingly slow speed versus typing. Eventually, I realized that the slowness was, as you said, a feature. It forces you to think . You have no choice but to take time with your words. Sometimes brevity is a gift (one I usually don't have). I migrated to fountain pens and haven't looked back. Partially, it's because I enjoy the experience…
Same principle applies to, e.g., Leica cameras. Yes, they're pricey (absurdly so), but the lack of features, the slow speed, and the lack of configuration contributes to me improving my photography. It doesn't make me a better photographer, but it gives me the time and space to focus on being one, rather than just firehosing my camera at whatever is in front of me. It makes my photography intentional rather than reac…
That is an experience you can't get any other way. That experience, also, pays forward in other areas of life.
I'm noticing the same thing with journaling. I still enjoy writing on my computers, of course, because I'm a much faster typist. However, I've noticed the deliberately slow pace of writing by hand has become transformative (slowly) over time. I'd imagine you're noticing the same thing. It's about self-improvement more than the hobby itself.
For me, it came at an opportune time: I started teaching an adult Bible study last year, and between journaling with fountain pens and teaching, it's forced me to get rid of some annoying habits that I might have held on to otherwise.