That depends on implementation. Shared libraries which use the same inode will be shared AFAIK. If containers use different libraries, they'll not be shared, of course, but that's a deliberate choice of container creator.

Containers can use the same base image for the OS.

I see these as a relatively straightforward set of problems to identify, quantify, and remedy. It’s a tradeoff between static memory usage and stability. If that additional memory footprint becomes an issue you can make plans to align dependencies.

And much lower chances of getting security updates, now that everything is a huge blob.