The Shield model without a thumb safety is (IMHO, of course) about as perfect as a small, slim, single-stack 9mm can get.
A single-stack 9mm Glock, the size of a Shield (or of a Glock42), would be an excellent addition to the marketplace, and likely every bit as "perfect"
Fans and purists will just have to have it. It'll sell well.
For those already owning a Shield or something similar, there isn't really a practical reason to trade or switch.