Not enough throw (orbit size) you need a lot of throw to polish anything with random orbit machines. The big boys are 21mm and the best all-around orbit size is 15mm. The Bosch, which you mentioned and which I have has a 2.5 mm throw which is perfect for cutting with 800-2000 sandpaper but woefully inadequate for doing actual polishing. The Bosch sander that will do it all is their version of the Festool Rotex which is their part number GET75-6N which is a dual mode machine having both forced rotation and random orbit.
Another case of if you what to play you’ve got to pay.