As much as it is a playerbase issue, few players spot targets, so support fire from planes, artillery, and mortars is usually delegated to guesswork.
Likewise, outside of the (overpowered) radio squad, radiomen are generally pointless to have around. They’re stuck in a limbo where either they can’t call arty often enough to be worth keeping, or they can call it too often, and I don’t think there’s such a thing as a happy medium with the timing.
Changing the way spotting works in order to benefit radiomen could be a solution.
First off, there could be a limited auto-spotting system. If you or a bot hit a target, any friendlies within ~25m will automatically see an indicator as it’s within yelling distance. Teammates outside of the radius won’t see those markers unless you manually spot, which will still work the same way it does now, preferably with a marker that differentiates it from auto-spotting.
Radiomen, meanwhile, could enhance the auto-spotting capability.
If you have a radioman active in your squad, everyone who also has a radio in their squad, including vehicles, will be able to see your auto-spots from anywhere on the map.
That way radiomen can be useful without being OP, and fire support becomes more supportive and less random.