If 3 people have died already then popping your ult (late) and going for a “hero play” is not the correct choice. Sure if it works you’ll get endorsed for it, but 99% of the time it doesn’t work and then you’ve thrown.
Similarly, learn to back up or retreat from a lost fight. Giving the enemy even more ult charge isn’t worth it.
Learn when you’ve lost a fight, regroup, try again next time. Stupidity isn’t the same as glory.
Depends, if your main healer is dead and you are going against full energy Zarya + ana its a 4vs2 but still makes sense to pop DB sometimes, unless e.g. your ana is holding nano. It depends but yeah, agreed with your statement. The sense for these situations comes with experience