The rewrite that never was
Edge was never a rewrite from scratch of IE. Not only did it share some of the same bugs, writing a new browser from scratch is a huge undertaking. Edge was IE without bits of shit like ActiveX. It had a new JS runtime and some other with bangs but basically built on the rewrites that started with IE 9. But without the lockin of ActiveX and no mobile base, it was obviously never going to be much more than the help viewer on Windows.
The IE team from IE 9 should be given credit for picking up the pieces of an abandoned project and working hard to implement web standards and continuing to do this with Edge. I think this means that Edge is a little bit more standards-compliant than Safari. Not bad considering where they were 10 years ago.