Youtube turned subscription numbers into a gameable metric for some time, so they got heavily inflated, so then Youtube basically made them meaningless. Youtube rarely even shows your subscribers your new videos nowadays, and for many creators, subscribers are about 20% or less of their total views.
In general it seems like if you keep ignoring videos from a given channel you're subscribed to, they will stop appearing most of the time in the default view despite the fact that you are subscribed, although they'll still appear if you go to the "subscriptions" view.
Basically in the default view I'm not sure it even makes much difference whether you're actually subscribed to a given channel or not; it seems like it's more about whether or not you've viewed the channel's videos recently.
I don't think it's unusual for creators who put out videos on various topics extremely frequently when most of their subscribers aren't watching every video.
It basically just means that the average subscriber is watching ~2 of his videos a month.
