I'll be obtuse, and claim it means "JavaScript-like". You know, multiple "truthy" values, the inability to detect the difference between arrays and objects, a weird mashup of OO and functional abilities, `=== undefined` but `isNaN()`, and no real difference between integers and floats, and all the math weirdness that goes with them. Browsers implementing the same thing different ways, interacting with a system (the DOM) that's the same but different everywhere, and patched together by multiple, usually-mutually-exclusive libraries that everyone uses instead of the actual language.

(disclaimer: I've come to quite like JS, it's made some of my experiments phenomenally simple. but it's weird.)

An API that maps to the underlying data-structure (btree, ranges, cursors), is bar-none simpler than an API that abtracts the underlying data structure away (like any SQL does).

The web was built by taking existing systems, and cutting away at them until they were so simple they barely worked. But because they were simple they could spread.

IndexedDB isn't the simplest spec it could be (I think they could do-away with transactions if they were willing to require MVCC semantics) but it is admirably simple for a database.