I agree. Whatever you replace it with will also need a careful setup and adjustment, and if you get it wrong it will work no better than what you have now.
There are four things that need to be precisely adjusted - the derailleur angle on the frame (outer edge of the cage must be perfectly paralell to the chairings), the height (outer edge of the cage should come within 1-3mm of the top of the teeth ont he big ring - no more and no less), the limit screws (must be set so the derailleur can reach the big and small rings without throwing the chain off), and the cable tension. IIRC, LHTs come with a friction shifter for the front, so there is a wide margin of allowable error in cable tension and you only need worry about the first three. Adjust them carefully in the order I listed them and the derailluer should work.