i try to steer people away when possible but unfortunately it's not always a possibility / worth the fight
One is the Search Console integration, which is the only way to see what Google search queries led people to your site.
The second is Google Ads conversion tracking and remarketing, which is de facto required to advertise with Google because it can easily 10x your Return On Advertising Spend, which is a key metric for digital marketing teams.
Without those two features, Google Analytics would be easy to drop. Many big companies already have other first- or third-party analytics tools they prefer. Many simply don't trust Google enough to send any commercially sensitive data, except where necessary to optimise ad spending.
They sell ads. The buyers of those ads want their ads on sites that have eyeballs on them. How do you prove how many eyeballs are looking? Analytics. If you write your own tool to generate those analytics, then even better!
G: We price our ads based on the number of visitors to a site.
Buyer: How do you know how many visitors a site gets?
G: Through the analytics we gather from each site
Buyer: How do I verify that your numbers are accurate?
G: ...