It will take a while, may be a long while, but one thing we can do is to switch to ...
No. This is a sociological or management problem: We need to change the way we allow people to work on mission-critical software, to make sure they are trustworthy. That means authenticating them (are you really the person you claim to be, please show us your ID card or driver's license), it means understanding their background (why do you online chat with a North Korean embassy employee who is known to be under cover), it means monitoring them (why are you taking a vacation in Moscow during the month with the worst weather), it means looking into their bank account (where did those 2 million yuan come from). In many software development environments (military and intelligence) that is actually done. While I've never been security cleared, I've spent an hour with a person from the government who works for a security agency several times, because they wanted to be sure (well, they also wanted to make sure I fill out my weekly time card absolutely correctly). In a civilian setting, this is done by knowing your colleagues as people, not as identity-less e-mail aliases. If the group of people who pulled off this hack had to come to work in an office with authenticated people every day (for example in the large Linux development groups that exist inside Intel, IBM or Google), their cover would have been blown within 5 minutes: There are 3-4 people, with thick Russian accents, and they all pretend to be "Jia Tin"?
Every third party software package put in its own protection domain and gets access to only what it needs and no more.
I'm not saying that this is a bad idea. Matter-of-fact, it is probably a really good idea. I'm actually old enough to have done some coding (in class) on the old Burroughs 5000 series machines, where each memory word "knew" whether it was an instruction or data, so it was nearly impossible to mistakenly execute integers or floating point numbers (known as a tagged architecture). I remember learning that there is also some hardware where low-level memory "knows" whether it is an integer or a string, which really helps find lots of bugs. I was there when the big micro-kernel discussions happened (and had the bad luck of having to use some micro-kernel based computers, which were barely functional). These are just a few examples of lessons from history that have been forgotten, and perhaps new designs (such as capability-based machines) will bring them back.
But we need to understand that this will RADICALLY change the way we code. Today, we build large pieces of software by simply assembling small pieces. As an example, the last few evenings I've been fixing my home-built backup software, and I'm currently using Python, C, parts of the Gnu C library (for calculating hashes fast), SQLite, GRPC, and probably a few other things I've forgotten. In an architecture with high walls between components, this will all change. The cost of transitioning to such a model is gargantuan.
And it doesn't solve the real problem: We need to trust people who are doing jobs where failure affects lots of others. There is a reason airline pilots and police officers are subjected to lots of scrutiny and background checks: it's because planes and guns are objectively dangerous. If an amateur wants to fly a small plane, or get a gun and do target shooting, they need to undergo extensive checks, and there is no room for privacy there. We need to abandon the computer culture's love for anonymity, and its pretense of a meritocracy (you are a good and ethical person because you wrote lots of correct code quickly).
May be there is some hope as I saw a recent White House report that is urging the industry to use memory safe languages as well as secure hardware building blocks such as CHERI or ARM's memory tagged extension.
All these things are a starting point. Where we can, let's use all the nice computer architecture techniques you mentioned. But we need to remember that ultimately, things like padlocks, keys, doors and safes are just there to slow thieves down; the ultimate way to prevent crime is to have a jail where burglars (once caught) get punished. At its core, this is a social problem, not a technological one.
