The old system I refer to was by submitting the flight plan to a FBU where professional flight planners would correct mistakes, something that at least 40 per cent had, correctly address it, initiate overdue action, provide advice and as ATC professionals made a system where the average PPL who has relatively little flight planning training, work.
I haven't seen or used the new AFPEx, but I would doubt very much if it's a simple "mask", whereby you fill in the blanks and hit submit. I would guess that the fields must conform to standard FPL syntax or it will be rejected. Maybe FlyUK73 can comment on this?
As for filing a FPL at ETD -10, surely a web based system could quite easily prevent such a late FPL submission? With the old system, there's nothing to stop someone sending a fax, whenever they like!