Everyone knows the meme of lee sin "Hit Q, take Q", but this isn't unique to lee sin. So many teams, especially at lower elos, seem to be under the impression that if they CAN engage, they absolutely have to.
Whether it's a Blitzcrank pulling a fed Renekton onto your ADC or Kayne hopping over a wall to ult a squishy who is dead center of his entire team while his own team is nowhere near close enough to assist, there is an issue of people just diving into fights without thinking.
Do you have vision or at minimum four members of the enemy team? No? Don't fight.
Are half your team's ults on CD while the enemy has everything up? Don't fight.
Is there a more important, safe objective you could rotate to and zone the enemy away from in order to secure a lead and potentially bait out an enemy for a pick? Don't fight.
Is a key member of your team nowhere near the fight? (ADC, Mid-laner, the only tank on the team, etc) Don't fight.
Does the enemy team have a significant lead? Are more than three enemies there? Are you nowhere near your turret? Don't fight.
Information wins games. People not paying attention to the game state, their teammates, vision, or objectives causes about 90% of bad fights. Simply put, if they would look at the information they have available, they would make a better decision. This is the reason LCS players often fight and die over wards.
"But Cloak, I'm not LCS and Neither are you, so [Generic Boards Insult, usually referring to Elo]"
Exactly. LCS players might have enough game sense to know where the enemy jungler is without seeing him on a ward. Most players do not. They can take a better guess at where the enemy might be simply by seeing where they are not. So this concept applies even more heavily to the average player than it does to them.
The number of games I see just thrown away because the team with the lead thinks they can just pick fight after fight after fight regardless of the scenario is mind-boggling. It's also where half my come-back games come from. The fed enemy champ just keeps diving in 1v5, we get the shutdown gold, we 5v4 the enemy team for an ace, grab baron, and win the game when we have absolutely no right to.
This doesn't seem like a concept that should have to be explained but even as I'm playing with low plat players in my matches, it's a thing I'm seeing daily.
So I will reiterate one last time. Just because you CAN fight. Doesn't mean you SHOULD.