I don’t think fourth edition was a mistake. I think the mistake came with their licensing fiascos; 4E was supposed to launch with a scratch-built virtual tabletop to facilitate global play but they botched the licensing and had to scrap the VTT, leaving 4e with a ‘jarring’ change of language with no context on those language changes due to the lack of accessible VTT tech dedicated to the edition. 

Frankly I think its Power system is clean, its mechanical uniqueness is refreshing, and its monster creation has been a major source of inspiration for my 5e homebrew. Heck, I use many things from 4e in my 5e games since I can’t find anyone willing to try proper 4e with me.