A few other platforms I have tested:

• AppGyver: this platform had a nice introduction when signing up. However, this platform didn’t support Google Maps and extending with custom logic seemed difficult
• Microsoft PowerApps: you can only sign up with a corporate email address (no gmail!) so pretty much a middle finger to us normies :(
• AppHive: while this platform doesn’t have a great onboarding experience, there are incredibly comprehensive starter applications. The application I tried was essentially a full-fledged Uber/Lyft clone complete with sign-up and 1:1 chat with the driver. AppHive uses pre-built functions for most common application flows. I think this is enough for most developers to create a login flow with mostly CRUD after that. Basically, your development flow is creating the callback flows to handle different event trees (transition to this page if data fails, …). I have not tried publishing to the App Store which is usually where most platforms suffer as builds are complex and the least user-friendly part of the application. The database side of the application is a bit clunky but it does the job if you need something working quickly.