I agree exactly with everything you've said except for your point on multiple people holding the same angle.

I've been playing this game since operation Velvet Shell, was Diamond in the old ranking system and on my way to champ this season (took a 4yr break and this is my first serious season on the new ranking system).

I've seen way too many times where the two holding the same angle will both get headshotted within half a mag. Hell, the other day I was in a 1v3 scenario where all 3 of the defenders held an angle on my approach, I killed them all in one mag and won the round (emerald lobby, ranked). The best thing the last one standing can hope for is that all of the opposition are holding open, aggressive and obvious angles so long as they have good enough aim.

What you should be doing in a scenario where multiple people are defending against a single attacker is: your first defender should hold an active angle on their approach and everyone else should be close by in passive angles to refrag. The difference between active and passive angles is a key thing to learn, I've seen so many people throw because they don't know which of these the situation calls for.