If you really want to get the shift back to normal then you'll need to overhaul the gear level mechanism itself. Mercedes sell a specific repair kit to do the job.
I’ve been told to replace the six bushes but mine don’t show any wear. Years ago I had a W124 with worn gear linkage bushes and the gear change was awful. Replacing the bushes transformed it.
What goes wrong with the gear change mechanisms? They look incredibly robust.