I'm with the OP on this. Life is too short to spend time at any place (eg an airport) scanning every notice to see if there is one that someone thought is all that is required to handle a situaltion. Any facility should be intuitive and straightforward.
Sounds like Manchester has done what a number of places (eg Edinburgh) have done. At the latter the rental cars were moved away from the terminal, so it is now either a 10-minute brisk hike, or a wait for the ONE bus which circulates to both the rental car locations and also the remote car park, which is just beyond, and takes about 15 minutes for the round trip.