The change to the lighting system from RAW 5e hasn't made all-darkvision parties weaker at all and the disadvantage in dim light is not fun to play. For example, in a room filled with Dim Light a full darkvision party can happily attack every enemy with no disadvantage at all. Any non-darkvision member can only attack with disadvantage unless an area is lit up. The area being lit up for their turn is entirely dependent on getting the correct Initiative order. This change was made so that all darkvision parties weren't as strong but they still are much stronger than a mixed party. There are ways to get around the dim light issue for non-darkvision characters, but the darkvision characters don't need to worry about those conditions. They are free to attack normally without any restrictions.
I don't know what the solution to this is, but currently having some members be really weak due to lighting really affects my enjoyment of some of the battles and can make them tedious and unfun to play.
Possible solutions discussed with Discord community:
1. More flammable objects in battles (for lighting purposes only)
2. A popup for readied attacks stating if you want to trigger the attack on a moving enemy (to help with the solution of getting an enemy into bright light who tries to move out of it)
3. The ability to cast Light on arrows (or perhaps light them by other means?). If the attack hits it could stick in the enemy, lighting them up. If it misses it could light an area nearby.
4. Buff non-darkvision races in some way to make up for the disadvantage.
One or more of these solutions could help potentially alleviate the issue. The issue won't be completely removed unless light becomes a non-factor, which doesn't seem like a solution the dev team wants to take.