My take is the reason why there is such an emphesis on specific experience (and not just being smart) is modern web apps today are very sensitive with a slew of libraries and frameworks built on top of each other, in a multiservice environment each with different flavors of technologies. Someone coming in fresh without any experience with all of the libraries and tech are just not going to success.
No doubt you have carefully curated and assembled the stack you have because it gives you a competitive advantage. But everybody else is also trying to get a competitive advantage, so nobody is going to have exactly the same stack, used in exactly the same way, as any other company.
Its true, programming has changed: we are building on top of frameworks and incorporating services today, and not doing so much development from the bare metal. But that doesn't mean that you can't hire anybody who isn't a clone of you: it means that the we have to train ourselves to have the ABIITY to just jump into a new stack, at a new company, and quickly familiarize ourselves with it.
THAT is the key skill going forward. The crucial skills are not can you remember how red-black trees work, or how to use dynamic programming to implement this algorithm. And its not whether they can put the right keywords on their resume. It's can somebody dump 100,000 lines of code in your lap and have confidence that you can handle it.
And also, if somebody can't join your team and be productively "plugged into the matrix" in a few weeks, that means your stack has some architectural problems: lets face it, even code you wrote 6 months ago might as well be brand-new code to you. The code base has to be such that it's easy for people to quickly read it and figure out what is wrong and how to fix it.
Otherwise, even people who have been there for 10 years using that exact same stack are not going to have any success.
