Every gun can be improved. The factory or manufacturer cuts cost by cutting corners. For you and I its a labor of love to dissemble our firearms and make miner modifications. For the manufacturer the modifications cost money and its passed on to you and I. They want to make it 100% reliable and cheap. So they skip some of the improvements for profit.
Find out what you want to improve. Go to you tube or ask on this forum. The metal in some guns can be "bedded" in the stock. Barrels can be "floated". Triggers can be improved for length of pull, creep, and pounds of pressure. Make sure you understand what you are doing before you do it. Make sure your gun is not loaded.
For all of my modern rifles I bed the action, float the barrel, lap all the parts, do a trigger job, put clear nail polish on all the screws, before I even load custom ammo for each. Many of these mods can be applied to your muzzle loader.