This is an argument taken to a naive extreme. You can't expect every business to also be in the business of analytics, it's not realistic. There's a reason companies have business partners who specialize in certain services.

It's why you have accountants, lawyers, marketers, etc.. Not every company can afford to have all these specialists on payroll, so you work with a service provider that lets you afford the services in a fractional way. You give them access to your data, including customer data sometimes, and in return they provide you with insights and information from that data.

Analytics is just another service provider like that.

You should of course work with a reliable and trusted partner that treats your customer data appropriately and has strong privacy guarantees.

The problem with GA is not "third party", it's "third party that uses my data for its own purposes" because that's the actual cost of using a free service.

Saying "no third parties at all" is not how businesses have operated since forever.