You are equating the removal of a bonus for ranged attack from high ground, with removing combat tactics. You have nothing to support your opinion, other than "you believe that high ground should give "some bonus", while completely ignoring the inherent benefit of getting to high ground, less chance of a ranged character being pulled into melee, and greater chance of maintaining concentration spells.
Getting to high ground does not make a person more accurate with a ranged weapon.
How does high ground help maintain concentration?
Indirectly, of course. If people on low ground have disadvantage to attack = less chance to hit = more chance to maintain concentration.
It can also be used to block LoS so enemy ranged can't attack at all by backing up. Some times arrows/bolts can still target you if the terrain blockage isn't enough for the arc, but most spells require a straight line LoS and won't arc up and over like that.
