What blobs is this guy talking about? Device drivers and/or the APKs that support them? Those have existed since forever. Google used to publish them to the AOSP repo. If they've stopped doing that, it's not that important, since they can be easily extracted from the system images, or from the devices themselves.
Google apps/libs? That's a growing problem, as more and more apps are starting to rely on those, hence MicroG.
One of the problems is that the blobs are preoptimized and stripped. You can see some of the crazy hoops people are jumping through to make AOSP work here, https://github.com/anestisb/android-prepare-vendor
What's obvious is that google isn't building AOSP themselves at all anymore and it's suffering from neglect.
He is talking about the possibility to build AOSP without certain propriatry (native) libraries that are used to communicate with the device components. While you always need them at runtime for a lot of features (but some devices run in wifi-only mode without prorietary libs) it was possible to build without them because of the way they're linked. This was changed in Nougat where it became impossible to build the source code for certain Nexus devices, because during build process there are references to the source code of some proprietary libraries. I had this problem myself while building AOSP for Nexus 5X and can confirm it.
Stuff like the VoLTE calling apks – those are now shipped as precompiled .oat libs, but CopperheadOS has to recompile them to get properly verified boot with the same key for all system APKs.
Google apps/libs? That's a growing problem, as more and more apps are starting to rely on those, hence MicroG.