Simplistic or not, doesn't mean it's a poor implementation. It's just a simple implementation. And as for FO3, come now, flanking and suppressive fire ? I didn't experience that from the Super Mutants (although they are supposed to be idiots), Raiders or Enclave. They did the same thing you'd decry FO2 for, go around corner, wait for them to round it and unload on them, easy does it. Wouldn't say it's a terrible implementation of FPS combat, it's a fairly simple one for this day - I'd hate to be playing old-school GR set in the FO universe, heh.
There's a section of broken overpass just north of Vault 101 which serves as a great sniper location to take out a batch of nearby Raiders. First time I tried it, one of the Raiders stayed at the bottom taking pot-shots at me with an Assault Rifle. I kept backing up over the edge to reload and regain AP so I could VATS her down with my Hunting Rifle. I'm like level 6 or 7, and the range is long enough that this is taking quite a while. One of the times I back-up, I get clobbered by the Lead Pipe guy.
Maybe I play too differently than you do, but I see flanking attempts (and am sometimes even caught by them) from Raiders all the time. In Mama Dolce's, I had a Chinese Sergeant run around the building in order to get a clear attack on my back while I was tied up with one of his buddies.
Even Super Mutants. I've seen Masters hold off on firing their Miniguns until the Melee Brutes had closed some of the distance. I've seen Super Mutants go for cover. I've seen the red lines marking where they are close in on me when I've taken cover - but never when they're armed with only Hunting Rifles - just the guys with auto-firing guns.
I've had all sorts of enemies open up with a grenade lob before rushing in.
Do I take advantage of the "come around the corner VATS ambush"? Yes I do. But I've also seen enemies refuse to come around that corner. It seems to work best if you get your Sneak state to [CAUTION] and not flashing [DANGER]. Doesn't that make a lot of sense?