Was it purely the extra time that killed the games in question, or other additinal factors? If a game has a great premise, is coming together well during the course of development, yet doesn't appear to be able to meet its given schedule, I can't see how affording the devs an extra few months of polish would somehow kill a game? If the game wasn't working at all, then of course, more time to polsih a turd will still produce a turd at the end of the day.
Time, or rather lack of pressure will kill a game, because teams lose focus.
Very few designers have sharp focus, everything is over designed, it's worse on large teams with many designers. Every feature you add is important to someone, so cutting a feature is a painful process, without time pressure what happens is features get added but never really finished. This can continue indefinitely as far as I can see.
When pressure finally is applied (sometimes years later) rather than cutting and distilling the experience what happens is teams try and ship everything at a reduced quality bar.
What this delivers is an unfocussed often shoddy experience.
I'll give you an example, I worked on a game where you could drive between locations in an action game, driving was really just a form of transport in the game, but because there were 6 designers on the project, one of them was tasked with designing it. He produced 60 pages of design, the vast majority of it superfluous to the core gameplay. To him the driving part of the game was the focus of the game, because it's what he focussed on.
Like films games need editing, and the designers/directors are often not the best people to do that. Without time pressure there is no reason to edit.
I think I said this here when E3 was cancelled, I hated it because of it's timing, but I'd seen it rescue games because teams were forced to pull things together and focus on the core experience.