Why not simply say "he's 5 feet away, you'll get +15 to your attack" or "the wyvern is 10 meters up, he's out of range for a bonus"? The players will look at the miniatures and say "Look, he's 1 grid space away that's 5 feet. +15 to my attack."
We play the RMFRP version. We also try to stick to RAW as much as possible, for consistency's sake. Movement distance has to be covered to determine penalties for movement. Flank has a different bonus than rear. Radius and range of spell effects need to be accounted for. Etc., etc.
All of these things really need to have a physical representation that can be seen and measured. You don't have to strictly use a miniature. A coin, a die, a pog, or anything else can be used to represent the PCs/NPCs. You don't even need a map or battlemat, a tape measure can do the trick just as well. But no matter what the medium, our group finds that some sort of "miniature" and "map" combination is necessary.
Tactics are a large and integral part of our RoleMaster games. And miniatures and hex maps are a key part of representing the tactical situation.
Not only am I not nearly good enough to keep everything straight in my head, but the players need to see the situation so that they can plan their actions.
But there are some game systems where representing the tactical situation in a physical manner isn't all that important. We generally don't use minis and maps for games in which the tactical combat doesn't have that much of a role such as World/Chronicles of Darkness, or in games where position and range doesn't make all that much of a difference such as Palladium or one of the super hero games.
So yes, there are some games where minis and maps aren't needed, or all that useful. But our table finds that RoleMaster is not one of them.
Besides, minis are just cool. And painting them is an enjoyable hobby all its own.
