Absolutely agree. I long ago became fed-up with the Lufthansa booking engine, and for anything but the simplest of itineraries (such as DUS-GVA return) I book through one of the online travel agents or a real one. I find orbitz has been quite helpful as of late.
Having said that, I don't really fly with Lufthansa any more, not on paid tickets (sometimes I use the miles, if the taxes don't exceed the cost of a paid ticket, another stupidity that I am surprised no-one has corrected yet). As for the booking engine, you'd think in this computer age and the time that has elapsed, that they would have tried to improve it..just a bit.
Really, it's just one of the myriad small and not-so-small things that have put me off the company over time.