I think this is so relevant, and thank you for posting this.
Of course it's trivially NOT true that you can defend against all exploits by making your system sufficiently compact and clean, but you can certainly have a big impact on the exploitable surface area.
I think it's a bit bizarre that it's implicitly assumed that all codebases are broken enough, that if you were to attack them sufficiently, you'll eventually find endlessly more issues.
Another analogy here is to fuzzing. A fuzzer can walk through all sorts of states of a program, but when it hits a password, it can't really push past that because it needs to search a space that is impossibly huge.
It's all well and good to try to exploit a program, but (as an example) if that program _robustly and very simply_ (the hard part!) says... that it only accepts messages from the network that are signed before it does ANYTHING else, you're going to have a hard time getting it to accept unsigned messages.
Admittedly, a lot of today's surfaces and software were built in a world where you could get away with a lot more laziness compared to this. But I could imagine, for example, a state of the world in which we're much more intentional about what we accept and even bring _into_ our threat environment. Similarly to the shift from network to endpoint security. There are for sure, uh, million systems right now with a threat model wildly larger than it needs to be.