The change in contract and nature of GPs probably has more to do with it that actual capacity, though clearly you can't squeeze a quart into a pint pot.
We really need to ask if primary care is to provide primary care, or as at present a cheap outpatient and community health service.
Almost all GP time is now spent on follow up and preventative care, rather than on acute diagnosis & treatment.
So are GPs being trained for community and follow up care, or primary care?