770/800 makes capturing points kind of irrelevant, the game went quite poorly all around at this point...

But still, if the victory wasn't so close I see the best point here would be to circle down to behind blues and kill them as they're charging Reds for that S-Rank. Thse 2 A-Ranks can be defended by the same side and the blues are clearly too busy charging the full force of reds to pay attention to a proper pinch in there.

RNG counts for only about 10% of a Seal Rock win (I mean, aside from the RNG that put you on a team of people that kill against a team of people that dies.) The other 90% is about raw destructive power of being able to win your fights and push the other teams around. The way I see it, yellows in that position are poking at the wrong angle, and attacking with way too little pressure for either red or blue to worry about it too much.

Increase your pressure, get some massive BHs going and the points from objectives will come naturally.