Some people just love proves of concept and the shiny next thing. I guess that role is useful, in its own way.
It's why many brilliant minds appear to be quite content working for unethical tech giants, advertising or surveillance companies.
The reason why the company exists doesn't matter to them.
What the company actually does outside of their computer doesn't matter to them.
The technology and their freedom to pursue the New does. Companies love the production and enthusiasm they provide and pay well for it.
(Usually these types of developers do have a conscience and it's often taken up, used and displayed in worthwhile and benevolent corporate friendly style social activism)
I see this as positive because computer nerds (I'm one) get to be paid very well to figure out the new and shiny. It's what I'd be doing at home anyway.
Most of the time nothing of value is created (Except my amusement), but every once in a while something brilliant is, and due to scale, it can have big impact.
Good specialist engineers designed gas chambers in Nazi Germany
Promos require promo packs, and promo packs require large beefy projects. (Good luck jack of all trades).
Thus, you end up with these situations where large beefy projects are solutions looking for a problem as the core problem being solved is a promo, not a business need.
PS. What you describe seems to be not even about PoC (the rule about PoC is that it should work at all), but about following the herd and inventing a setup to appear busy. But that'd be also not very good environment to stay at, as an employee..
The problem is that companies take a Java 5 monolith without any CI/CD and want to take rewriting AND re-platforming AND business changes all at once in a giant project. Then they pick the technology that is anyone might be blaming and run with that excuse so it's nobody's fault.