I don't have a problem with high ground Advantage currently. Even used against the party there are obvious counters to it.
I was glad to see the end of backstab advantage to be replaced with simple Flanking for sneak attacks.
It never made sense that you could run behind an enemy and sneak attack them if you were the only one there. It DOES make sense if the enemy is flanked that you could do that.
Does a ranged attack gain advantage when an enemy is engaged/flanked by one of your party members? Or would you need to be able to do a Bonus Action Hide in order to gain advantage and sneak attack from range if Height Advantage was removed?
Backstab Advantage wasn't replaced with anything. Flanking allowing sneak attacks was already in the game, just never noticeable because you always could just get backstab advantage.
Ranged attacks don't gain Advantage when an enemy is engaged by one of your allies, but you do get sneak attack. To get advantage with ranged attacks without height, yes you'd have to BA Hide or use some other ability/spell.