Skipness One Echo..
As you well well know pax do self transfer & therefore do not feature on your particular selective radar.
You do have an issue with shops getting in your own particular way in terminals.
Perhaps other less frequent travellers than your good self may regard the shops in a different light?.(You are too young to be so jaundiced).
With your business acumen would you care to reflect on the scale of the rents the retailers are handing over to the airport operator ? which surely points to the fact they may be quite well patronized by many of your fellow travellers.
I`m glad you subtlety state "new" LHR terminals, as my first experience of the issue was T3.
Anyways Westfield (the real one) is a v v successful business enterprise as is STN today as you well know.It pays & has paid many many bills.
Although I could agree & trade you endlessly regarding the original concept & iconic design of the terminal I would rather have 2017 than when it opened to a hushed cathedral atmosphere with 1m pax per year!.