I think that depends on the circumstances. The peak here is like a million times higher than anything I've ever seen on Reddit (possibly I did not look hard enough:-). The average is probably lower, but even that depends on your instance.
One aspect is that Reddit had (has?) more niche communities, which by their very nature may be of more interest to you, and depending on the niche and community, that may remain on Reddit, have moved here somewhat, or elsewhere like Discord or forum boards/Twitter/Mastodon/etc., or just more or less ceased to exist altogether (possibly in a more complex way like a large fraction of content creators post nowhere now).
Also the presence of high toxicity - on Reddit, or here, or wherever - runs people off too. So burnt out moderators (or doesn't Kbin entirely lack any moderation tools at all?) means fewer comments overall.
This.
I also choose this guy's wife
And my bow.
"Overall" comment quality maybe should not even be measured evenly across everything when you can easily digest ones like these, but what looks like longer ones yet that contain misinformation are much more damaging to your perception of a place and overall feelings of love or disgust for it.
Finally, another aspect is that Lemmy/Kbin requires much heavier investments from the users - to choose an instance, a community, and curate your experiences in them. But once you put in the work and know how, it should get much better!
I am sure that I offered little in the way of actual solutions here, but I hope you enjoyed these thoughts at least:-).