It also focuses a lot on providing fast iteration times. You can hot-reload changed assets onto a device while the game is running. For most asset types, you'll see the change on device in less than a second. Similarly, a Build and Run cycle from scratch for a moderately complex game project such as Blossom Blast typically takes around a minute or so, and subsequent cached builds can start in a couple of seconds.

(Edit: Full disclosure, I worked on the Defold editor.)

When I used Unreal Engine, I found and fixed engine bugs.

When I used Unity, I found engine bugs and we had to work around them with ugly hacks.

When I used Defold, we shipped without ruining into any trouble.

Of course, Unity and UE are much more powerful. But if you don't need that, simple is king.