The company I work for (more or less B2B SaaS) does everything quick and dirty. Good gut feeling brought them far, but there is next to no data apart from total

The company I work for (more or less B2B SaaS) does everything quick and dirty. Good gut feeling brought them far, but there is next to no data apart from total sales and some basic google analytics. Stuff like A-B testing is far away. Has anyone had a similar situation? How to handle that? I'd love to do estimates and proof them right or wrong. But bundled feature releases, marketing and season all end up in the same number of "total sales this month". So far I did not manage to make them at least track churn/retention in a detailed way.