There are some big problems
with A/B testing
You need lots of time and traffic
A/B testing takes hundreds of visitors and weeks (if not months) to achieve statistical significance. Lots of campaigns don’t even run that long, making it tough to improve fast enough to make a real impact on your performance.
You can only test one variable
Each element you change—your headline, your call to action—is a new variable, which means you can usually only test one thing at a time. (Or you can run really, really long tests with multiple variants.)
You’re not actually optimizing yet
A/B testing randomly sends visitors to each page in your experiment—regardless of how they’re converting. That means you could be sending folks to an underperforming page for weeks while you wait for the test to end.