I went to see if I had any replies to a comment I left on a video for the first time today and it's really hidden to get back to them if you don't remember the exact video. I wonder if it's purposeful friction or just not a priority.
In my case I have almost all notifications disabled so maybe there's an option somewhere. Generally find those notification badges too powerful for me to not check and then get waylaid doom scrolling/watching, so I've made it a habit to always disable them everywhere.
Somewhat tempted to re-enable it as I only really comment on videos that are for very very niche communities and I'm usually answering or asking questions.