For example, there are a number of fledgling open-source nonlinear video editors (NLEs) -- to name a few in no particular order Kdenlive, Openshot, Olive, OpenMovieEditor, Blender Video Sequence Editor, Shotcut, Cinelerra, and Flowblade. I say this with full respect to the authors and contributors to those projects, we just need ONE open-source NLE that is on par with Final Cut or Premiere Pro.
But we really can't blame the authors - there's no money in open source user apps and polishing isn't fun to most people. I'd immediately jump on the opportunity to build an NLE from scratch if given the time and financial freedom, but I can't see myself digging though someone else's code and sanding all the rough edges for fun.