I think many people in this thread are making the mistake of ignoring evolutionary factors in system engineering. If a system doesn't need to adopt or change, lots of things can be much more efficient, easier and simpler, likely the order of 10x~100x. But you gotta appreciate that we're all paid because we need to swap wheels on running trains (or even engines in flying airplanes). A large fraction of demand for redundancy, introspection, abstraction and generalization comes from this.
Why do we want to apply ML at the cost of a significant fleet cost increase? Because it can make the overall system consistently perform against external changes via generalization, thus the system can evolve more cheaply. Why do we want to implement a complex logging layer although it doesn't bring direct gains on system performance? Because you need to inspect the system to understand its behavior and find out where it needs to change. The list can go on and I can give you hundreds of reasons why we need all these apparently unnecessary complexities and overheads can be important for systems' longevity.
I don't deny the existence of accidental complexities (probably Twitter can become 2~3x simpler and cheaper given sufficient eng resource and time), but in many cases you probably won't be able to confidently say if some overheads are accidental or essential since system engineering is essentially a highly predictive/speculative activity. To make this happen, you gotta have a precise understanding of how the system "currently works" to make a good bet rather than re-imagination of the system with your own wish list of how the system "should work". There's a certain value on the latter option, but it's usually more constructive to build an alternative rather than complaining about the existing system. This post is great since the author actually tried to build something to prove its possibility, this knowledge could turn out to be valuable for other Twitter alternatives later on.