*A Shoutout to CRO Experts* What Not To Do?

Don't Do CRO If Your Conversions Are Less Than 500/month, said a Global CRO Expert!
All of us want to continuously increase our conversion rate, even a percentage jump can compound into a humongous number in few months. As small teams, we also want to improve but the A/B testing tools often take ages to respond and give us test results.
The expert advice I received is to trust my guts, again and again. Make changes measure and assume it was because of what you did. Data will not be help 100% accurate.

Do you think this is correct? What is your learning? Is there a tool that focuses on a small sample size for testing?