One could still use Google Analytics by proxying the tracking events. Afaik only the IP is considered private data. So one could mask or (non-reversibly) hash the IP, remove anything else which might be considered private data and then send the event to Google. A simple PHP script with a few lines of code could do that.
But Google lost me by:
A) Making it impossible to convert your old data into the new Analytics version
B) Abandoning the API which allowed you to code your own reports. Over the years, I wrote a ton of code that talks to the API. This is all worthless now.
I recently switched to self-hosted Matomo. At first I did not think much about it, but now after I got used to it, I have to say it is much better than GA. The interface is so much nicer and snappier. And more logical.
Apart from that, I like that it is open source. If there ever is a point in the road where the makers of Matomo decide on a non-compatible fork, I'm sure the community will write a converter that converts the old data into the new format.
And after using it for a while, it hit me: You can write your own reporting tools by just querying the MariaDB database! Using SQL is so much better than it was to fight the insanely complex and unintuitive Google Analytics API.
If I really wanted to still use Google Analytics, I would just write a converter, which pumps all the Matomo events into Google Analytics. That would be a GDPR-compliant way to use Google's tools. But I don't. I'm done with Google Analytics forever. Matomo is the promised land for me.