actually, it was made so melee champs can keep up with ranged champs kiting them.
That was not why it was made. The expressed purpose was to give AD carries choices in their itemization by allowing them to give up the damage of the other zeal items in exchange for better safety against melee assassins and bruisers.
Only ranged champs having this would literally be the death of melees
Major exaggeration. It's already being used primarily as an item for ranged champions with a few exceptions. It would hurt a couple of champions to have it be ranged only, but most melee champions, particularly bruisers, would be unchanged.
Mind you, I'm not saying that having it be ranged only is a good idea. I don't think it is a good idea. I'm just saying you're blowing this majorly out of proportion.
bruisers don't have mobility
Plenty of bruisers do have mobility. Renekton, Vi, Jax, Irelia, Hecarim, Jarvan, etc. Just saying "bruisers don't have mobility" is patently wrong. A small subset of bruisers lack mobility (the juggernaut types), but most have it to some degree or another.