GCP is 2 years behind in versions and the funky setup around connections is a hassle to deal with. The number of connections is limited and not configurable, and the default way to connecting is to use the Cloud SQL Proxy which is a separate binary/service you have to run to connect.

Public IP access is available but that means going through the public internet, and also means you have to whitelist each individual IP accessing it, which is hard or impossible when trying to use ephemeral or private-ip-only instances.