Why AV is ruined at the moment! Why alliance can't win!

Well, I didn’t say every clash, just an overwhelming amount of them.
While what you say is indeed a problem, what you didn’t mention was how even if there’s an evenly numbered huge clash, there are, let’s say 80 people to simplify the example, all doing things at the same time, and not everyone is in range of everyone else during the entire time of the clash either. So positioning plays a part as well, which every RBG player can confirm for you.
Not everyone has AoE to spam as well, some are better single target and so on.

Eventually, it comes down to what I mentioned earlier:

Let’s say 1 side scores 5 HKs before the other side scores 1, early on in a clash. This affects the overall amount of sources producing numbers like damage output and healing output and so on, from that point.

And we all know the effects these things can have.

Then there are playstyles that are different, and it’s basically a melting pot of an insane amount of variables that together ends up deciding which side beats the other in a huge clash which opens up the way to reach objectives and so on, and to basically apply pressure.
Then there’s such a thing as overextending as well.

PS:
This is also the reason why SH gy being closer to the first clash is by design an advantage, however player perception has misconstrued it as being a disadvantage.
Because when the PvP clash ends up “even”, where you basically get to score 1 HK for every player you lose on your side at the same time, the alliance side will replenish their numbers faster than the horde side due to SH gy being closer to that first clash.