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 reactive.
I think you just explained the opposite—that, yes, it does make you a better photographer. You've just described everything that it has done, which is continually improving your skill set and your thought process(es) that go into your creative work. Now that I understand the process, I love reading stories from others who have learned the same lesson: Deliberate slowness gives you time to think, time to plan, and time to breathe.
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.
