The slowness is a feature, not a bug. It gives your brain time to chew on it a little bit, digesting the information and storing it away instead of just copy-pasting.
Speed-hacks like shorthand and stenographers' machines are for copying exactly what was said, not consuming and understanding it. I would be very surprised if there were not very old studies moldering in a paper journal somewhere investigating the information retention of secretaries / stenographers compared to "naive" note-takers.
+1 Deciding what to write is the critical step. You can get it with careful typing, but it's harder because you can type fast enough to skip that step.
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!