Further, in some ways it's the "lowest common denominator" (so that it can be easily implemented on top of each "underlying" graphics API), with union of all their downsides and only intersection of upsides.
WebGPU brings some important improvements that are simply impossible to implement with the WebGL programming model (such as moving all the expensive dynamic state validation from the draw loop into the initialization phase).
It's not perfect mind you (e.g. baked BindGroups may be a bit too 'rigid'), but it's still a massive improvement over WebGL in terms of reduced CPU overhead.
obligatory xkcd: https://xkcd.com/927/
Instead we have a third graphics standard (after canvas and WebGL) fully incompatible with the previous two that does exactly that: abstracts the OS graphics stack in a new layer