I don't understand the premise, is this saying short form posts (dare I call them Tweets) on Bluesky are somehow a replacement for long form blog posts?
No. atproto (which is what bluesky is based on) supports all kinds of public media - for instance https://standard.site/ which is designed for longer form static content.
You can choose where your PDS runs and the ecosystem still works. If one relay shuts down (Google Reader) or takes their API private (X, Reddit) it shouldn't matter, the PDS are separate and another relay can take over.
Worst case you can go directly to the PDS, but that wouldn't work at scale
