I'm sorry, but absolutely nothing justifies lethargic play. Lethargic play is very much against the rules and can be reported. The only time it's justifiable to give up is when the enemy is inside your spawn point and farming you as you revive, which is impossible to do in this game.
Premades are more coordinated than your average player, but that still doesn't make them invincible. The people who repeatedly die to the prenades are as much a detriment to your team as the enemy premade itself.
That said, there's nothing wrong with dying to a premade dive, even highly experienced FL players slip up sometimes. What's important is a willingness to learn and having your map open.