I don't think so. It would certainly help in some specific cases and some ideas are certainly worth testing out. However : -A/B testing can only answer some very specific questions. Good UX is not just measured by engagement. -some of these decisions are just bad practices that are widely recognized : for example we were asked to add modal popups pretty much everywhere. -we are severely shorthanded and implementing these changes and the A/B tests can be a very significant time investment. Especially when they are abandoned before going live for the reasons given by everyone but the person in charge.