You’re right - having multiple copies of everything is a drawback of housing each application in its own container or VM. The standard rejoinder is that disk space is cheap. The validity of that rejoinder depends on what you’re doing and what hardware or budget you are working with.
Another problem is that old versions of these dependencies will be baked into an image that is then used for many years without updates. This ensures the application keeps working without being disrupted by an update to a shared library, but it also means things like security flaws persist. Arguably, this is mitigated by only that image having the problem, but one insecure app can be a real problem - especially when it accesses shared resources - and when the same problem applies to many applications.
Compiled code optimized for a specific system’s hardware is less relevant than it used to be - even Gentoo users do not focus on this anymore. Rolling your own container isn’t much harder than compiling with your own options.
The post volume is still much lower, but that isn’t all bad, since the toxicity and quality isn’t as bad and unlimited scroll time isn’t healthy.