I've been running a production project in Google App Engine for three years with six figure active users and can mostly agree with this. A few comments:
1. Stackdriver gets a bad rap. Maybe there are better solutions out there, but it hasn't been our weakest link. It's gotten very expensive, though.
2. Google recently deployed a new HTTP load balancer that is way better than the old one.
3. Instance usage on app engine is a little opaque and very hard to tune. A lot of it is trial and error.
4. Cloud SQL is garbage and the author is being generous if anything. Haven't had a chance to try Spanner, but it seems a lot better. App Engine + SQL has a lot of little hidden gotchas that are impossible to debug. I'd never recommend anyone use it in production.
Google Cloud has come a LONG way, and one of the biggest reasons we continue to invest in it is they keep improving based on feedback. Their product team is very engaged. Their IAM additions, improved load balancing, and additional availability zones have been huge for us.