Strategic understanding sounds like some big, complicated morass of stats tables and figurines being pushed round a map in a dusty war-room somewhere...it's really just about common sense!
Team 1:
The opposition had picked early and gone with:
Centaur Warrunner 
Death Prophet
Zeus
Leshrac
IoWe already had a
Nature's Prophet and myself as 
Beastmaster. It's pretty obvious from their line up that they're going to have to go for a hard push strat - they have no real carry and at least 2 heroes who excel at taking towers. My team promptly picked up 
Nyx Assassin, 
Spectre and 
Lich. The last two especially are horrific picks against a push lineup.Imagine how different the game would have been if we had
Tinker, 
Alchemist and 
Keeper of the Light? Or if Nature's Prophet hadn't automatically gone for the 
Hand of Midas cookie-cutter build?2nd Game:
The opposition got several early randoms and picks, showing a lineup of:
Troll Warlord
Morphling
Mirana
Vengeful Spirit IoI picked up a
Shadow Shaman thinking we'd need some lockdown to deal with Morph and Mirana, and some pushing power to stop the game going too late. The next two picks were 
Lifestealer and 
Dark Seer...ok not too bad, some reasonable carry and more push/teamfight. Final two pickups - Nature's Prophet and Tinker...not necessarily bad pickups, but their global push would definitely be crimped by Io turning up with a carry in tow.We got some good early success, grabbing some kills and tier 1s while getting the better of the farm/xp. Then we lost one 3v3 fight at a tier 2 and after that nobody was prepared to venture across the map again - "We can win because we've got great split push". I pointed out that
Troll Warlord plus other half decent carries will annihilate you late game. Sigh...inevitably the game went late, they grabbed an aegis and smashed through our t3, rax and ancient in less than a minute...Do you ever struggle to make picks when playing pubs?
Or would you like the chance to rant about some of your recent team's choices? :)
Ah, the old days.
Anyway, at least the
I always try to be the last one to pick in pubs, although I do always end up playing support. Although I did go to the higher bracket and play before, the situation are always the same. Some (probably most) will always go for the cookie-cutter build without thinking it'll work or not.