There is an answer to retention - customer service.

Retention can be recovered after downturns if you establish trust. To do so requires putting all attention on the customer. That doesn't mean A/B testing and user interviews, or other product mechanisms of customer focus. It means first-line customer service. It means that when people call with problems, those problems get resolved quickly, reliably, and don't recur. And it means having a human give direct responses, so people can build one-on-one trust with the people who actually solve the problems.

It also means having a phone number to call in the first place. Emails and other contact methods are fine, too, but you have to have a way to instantly talk to someone you trust. Many startup/SaaS companies are skipping that entirely, or giving free tiers where support is not included, etc. Yet every company I've worked at that had a direct support mechanism also had high retention. And the retention is 100% tied to the quality of the work done by the people who answer those calls.

I'm sure people have good business reasons why the energy and funds are put in other areas, and that is everyone's own choice to make. But it is no mystery of how to fix retention - offer world-class customer service.