A few new talking points to chew into.
First, crossrealm. I saw this briefly mentioned and wanted to say why i believe it to be a terrible idea. One of the most enjoyable aspects of vanilla pre xrealm bgs was carrying over guild hatreds, or realm forum vendettas into BGs. You’d rarely see people on your KoS list in the open world, but if you and they pvpd a bit, you were very likely to see them in one of the BGs. This made for some fantastic rivalries. My rogue hated coming out of stealth in AV because once those cooldowns were blown, i was a free lunch. Even if i had vanish up, i was still a free lunch. But i cant describe the pure joy of getting round behind the alliance zerg and pouncing on someone from the forums. Sure, it was a murder-suicide, but the satisfaction of seeing them go down made it completely worthwhile. If you never played pre-crossrealms or skipped the realm forums when they were smack talking hell and not just guild recruitment forums, you might not see this dynamic and wouldnt genuinely understand why it matters. But it really did. It was one of the most enjoyable aspects of guild and realm identity.
On the zerg 1.5 or 1.12 and the teaching issue. Obviously outside of premades (which were basically queue cheating (all click on a countdown in voice coms) if i remember right for AV and werent integrated for the majority of vanilla), it CAN be done.
I think almost everyone on forums knows how to shut down an alliance or horde zerg in AV right now. Every single player could rightly point out that you stick 5-10 people in IB to slow down the zerg, then use another 10 to hold them at the choke in relief hut. Let them cap sf, use the other 15 or so to recap ib and sh and a few rogues/druids to cap and hold sp, now the alliance is split, your team is respawning around their forward advance until IB/SH cap and then you move up the map pushing them further and further into their own territory. Its just a case at this point of pulling down the bunkers and crossing that bridge of death.
Now everyone knows how to win. You could make it so theres a test and they cant queue without a passing grade. But i guarantee you, the second they join the BG they’ll give zero concern for the overriding strategy of the battleground and go do their own thing. That’s issue one. You could teach pugs till youre blue in the face how to win av. But its just NOT that important. This isnt a raid boss. Win or lose you get stuff.
Point 2 is more interesting: I made this post around post 400. Its reasonably long, but it comes down to this: The incentives in AV 1.12 strongly encourage neither winning nor losing. They encourage honor/time. That means if you are going to win, its always better to win quickly and if youre going to lose it is always better to lose quickly. Prepare yourself, oh leader of the horde for the amount of people telling you to “shut up” in chat and “ffs! just let them win”. You can tell them the greatest zerg strat in the universe, but if it fails, god help you. You’ll see people talking about it for weeks in every other AV join: the mythical AV where horde turtled, still lost and wasted everyones time so ‘ffs just let them win’.
Point 3 is also interesting. In BC they recognised AV had serious issues with engagement. Horde were at a reasonable disadvantage. The bridge of death was way more tricky then the RH gates. Pallies on alliance were faster than anything on horde (obviously fixed with BE pallies in BC), the bunkers were harder to cap than the towers, and finally the starting cave was effectively further from the center of the map. This meant a small contingent of alliance could race to the RH, pull it down, then despawn the warmasters (known exploit), and be joined quickly by the rest of the alliance zerg for the take down of drek. So they changed the overriding mechanics several times to balance this out. Now alliance were on the receiving end of thumping horde wins as they backcapped towers and played strategically whilst alliance kept trying the old strategy. Eventually it evened out more, and thus modern AV was born. Games were more even, but pvp was totally marginalised. It really became a pve race with minor tower skirmishing. Im not here to talk about the pros and cons, but only to draw attention to the fact that blizzard had long known the damage 1.8-1.12 AV had done to the battleground and looked at ways to improve it. But at this point in time they were very much following a guiding philosophy of in and out playstyles. One where players could come home on their lunch break, grab a few dungeon runs or BGs and go back to work. So of course their solutions to those vanilla issues were built to address the long drawn out battles.
But a fair question might be whether this playstyle suits the overriding philosophy of classic which appears to be a back to basics of long drawn out time commitments and player interaction with other players. Would a modern 20 minute emp run fit in with the philosophy of classic for example? Of course not. It should be 72 hours long just like tyhe old days and nothing less 
Yet pvp is still being treat with the same modern aesthetic to the game. And though completely fitting with vanilla (where pvp was always a secondary concern to the developers), it does feel a little unfair now that they know how passionate that community is.
So the overriding issues in summary: The philosophy of classic is to get players interacting again and create that living breathing mmo world. Crossrealm BGs undermine this, as does short pve battlegrounds. However as mentioned earlier in another post, that isnt to say 1.12 is awful. Were the incentives in the BG looked at seriously and changes made to encourage player v player over player v end boss, they could just as easily deliver an AV the vast majority would be satisfied with.