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 itself as much as writing, but partially it's because they've forced me to become even more deliberate.

I'd highly recommend it!

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.