Argyle King
Legend
Not really. If there's no light, then that means that the denizens can also see in the dark. If there is light, then you are more easily seen once you get into it . The monsters are rarely going to be standing out in the open at a distance of 60 feet away so that you can see them with dark vision and plan an ambush.
The disadvantage to perception is far worse than the off chance that you will see a monster from 60 feet away and get an ambush in.
Not necessarily. It's possible that the enemy is using light sources but you are not. It could also be the case that the environment does have light, but the darkvision party snuffed the light to start the assault.
I don't assume the monsters are standing out in the open. Having terrain to traverse helps the darkvision party use stealth and tactical movements.
It's nowhere near the most power 5e ability, but darkvision certainly is a force multiplier. It's actually even better than modern night vision because suddenly being introduced to light does not in any way negatively impact a character with nightvision.
It is still prudent to carry a light source for when it is needed (just like a melee character should still carry a ranged option).