AngularJS is a prime example. Two-way data was a solved problem until people realized it wouldn't scale. Single Page Applications solve a lot of problems (ex b

AngularJS is a prime example. Two-way data was a solved problem until people realized it wouldn't scale. Single Page Applications solve a lot of problems (ex better UX, offloading load from the server, better separation of concerns) but they introduce a lot of new ones (ex SEO, UI unresponsiveness, etc). This is the steady and painful march toward progress. Add new functionality, identify the weaknesses, ditch the useless functionality, recycle the good parts and start again to test new assumptions.