I think the Shield is a very intelligent and clever piece of design, engineering and marketing.
It comes after the success and reputation of a top pistol line from a company with a solid background in producing good guns.
The grip is one of the most ergonomic I have held. Sculpted. The Shield did not compromise on the grip, just for the sake of smallness or trying to make it Into the pocket pistol market. And even more intelligent, they give you the option to extend the grip, to make it almost full sized and mor comfortable.
In extending the grip, and giving you the second extended magazine, they negate the argument that you are not carrying enough round. 7-8 is fine for all affectionados of the 1911, so, if you are designing a slim, modern 9mm, you must believe that 7-8 rounds of good SD 9mm will meet most customer needs.
And then the trigger. The stock trigger is nothing to write home about. But everyone knows that for $45, this situation is solved with an Apex trigger.
Finally, since you might assume that just about every customer might put a 4.5lb apex trigger on....a safety would then make sense to a significant segment of the customer base.
Add in a good warrantee, customer service, good manufacturing to make a pistol that is accurate and shoots well. Nicely balanced. And then price it less than your main line of service level pistols.
But, all in all, I think the smart move was not trying to force it to be a pocket pistol. Too many compromises there...which....IMHO....is one reason the Shield is more popular than most on the list above. I also think there is a move away from pocket pistols, back to slim pistols that are carried on the waist.
And keep the price low.
Just my observations.
Best
J