Ehh, PHP fits that bill and is clearly optimizable. All sorts of things worked well for PHP, including the original HipHop, HHVM, my own work, and the mainline PHP runtime.

Python has some semantics and behaviors that are particularly hostile to optimization, but as the Faster Python and related efforts have suggested, the main challenge is full compatibility including extensions plus the historical desire for a simple implementation within CPython.

There are limits to retrofitting truly high performance to any of these languages. You want enough static, optional, or gradual typing to make it fast enough in the common case. That's why you also saw the V8 folks give up and make Dart, the Facebook ones made Hack, etc. It's telling that none of those gained truly broad adoption though. Performance isn't all that matters, especially once you have an established codebase and ecosystem.