(5.) is the key to the the issue. So many players are strategically clueless in IB and Control matches. The losing team usually has 3 players with 0 or 1 Capture in the match
And Bungie created the Hunt mechanic in IB to punish teams who do not play the objective by increasing the advantage of capping zones, and they still do not get it!
It is not about only slaying, or only capping. It is about having the awareness of when you need to re-capture a zone as a team, and when you need to urgently stop the opposing team getting control. All the information is there in the match to let you know but so many ignore it
If delay spawns weren't in control then this problem wouldn't be much of a problem. Because players would know if you don't cap flags you will be lock out from capturing flags for a few seconds and taking out delay spawn will also make it harder to triple cap.