Those are all fair responses. I guess I just haven't seen much uptake of those new features among the Substack writers that I follow. When they do podcasts, they're hosted by ACast, SimpleCast, or one of the other podcast hosting platforms out there. Videos are hosted on YouTube (like everyone else's).
I would prefer if Substack spent more resources on improving its "core" newsletter/blog experience, but I can understand, given their status as a home for controversial writers, their desire to be a self-contained service.