In the past 12 months I've actually started running easy vs spamming out junk miles and seen a lot of improvements - some no doubt also from still being relatively new and from following a plan strictly. That said, I've got a few friends who are either running, or have run plans like Pfitz, who'll do a couple of general aerobic runs.
An average week for me has 2-3 doubles in, 1 speed workout, 1 tempo/threshold workout, 1 long/longer run. As no tracks are open I run to/from the workouts - so easy pace. The day between the workouts is normally easy pace too, as is the day before and day after the long run. If I run 7 days that leaves 1 run that I can do as a GA run.
I haven't yet read Pfitz (its on my list after Running with the Legends) but I'm aware that the GA pace stuff gets whittled down as you get further into the cycle, so I'm sure my friends are just early on or just base building whilst no races exist.
However I've tried running at GA pace a couple of times and it fucking sucks. It feels like I'm pushing too hard and my HR is too high for the speed I'm moving, and I feel far more inefficient than I do at a tempo pace.
Whilst I may never do a Pfitz plan, it has got me worried that I've done too much easy running and I now just default to that pace. At the same time I remind myself that the only important thing at the end of the day is that I can hold a pace during a race. Is it possible to do too much easy running and just default to that pace?