And I will need to buy a new phone just to get this patched up... "Too stupid to be stupid". Why google didn't design Android to be hardware agnostic or just forced manufacturers to opensource their drivers?

I think it's on purpose - ultimate "planned obsolescence", we got our removable batteries, so they needed to create another reason you must upgrade once every few years.
I'm a developer (although not "low level"/OS so I maybe wrong on that) and I can't imagine why I can't just flash new android os, then flash a device specific configs and drivers from a zip provided by manufacturers and I'm updated? That's how pc's roll for years, its little messy and error prone sometimes but did you ever heard: "I must by a new PC because of newly discovered os vulnerability"?