The answer is fairly simple, the owners closed up under threat of possible litigation, the community & especially KM have worked hard to keep it going, & to make improvements, removing fakes from search results is a BIG improvement.. but you have to understand, the code for winmx isn't available & improvements take time & talent, we're VERY lucky to have the talent of KM who has indeed devoted his time to it.
I'm sure I'm not alone in finding the removal of fakes to be the biggest improvement that could have been made, WinMX is the ONLY p2p network where this problem has been beaten & i know that ways to beat the isps who throttle p2p apps into inoperability are under consideration, both of these seem way more important issues than the flashy new interface & version numbers other apps might be sporting.
Good software is software that WORKS, not just looks flashy