Zapier is useful for integrating common tools (slack, drive, asana, etc etc) but would not be a good choice for most nontrivial ETL, or nontrivial any kind of integration.

Eg, you want a slack notification when a Google form is filled out. Pretty painless to set up a zap.

You want to keep a database table up to date with a Google sheet. You can do it on zapier, but it's gonna be a pain.