Making big, sweeping changes can be highly ineffective. That’s because you won’t know which change made the biggest difference.
For example, this could mean that just one aspect of your product messaging is changed initially so that its influence on sales and leads can be studied. If you were to change your product description, headline, price, and checkout process all in one go, you would never know what was driving the improvement (or where you continue to miss the mark).
A/B testing allows a couple of small changes to be made and compared, so the best performing option is clear. That can then be refined further to arrive at the best possible version.