That isn't even slightly comparable as those plugins required the end user to install them, due to the inherent security concerns. Contrast that with today: you are constantly using websites which require giant libraries that entirely subvert the underlying semantics, such as React... it isn't at all crazy to just stop adding more BS to the browser and require more of it to end up in rendering layers such as React, or even to long for a web where React is merely built on top of something like canvas. (FWIW, Flutter is like this, and it is actually pretty damned good; it isn't great, but if we concentrated on only adding features required to fix Flutter's complaints, the web would be better for it, and we'd see a ton of web browsers as a handful of people can legitimately build an operating system kernel or a language compiler or a virtual machine monitor or a CPU emulator or a 3D engine, and yet implementing all of the current web stack requires some giant company, which is ridiculous.)

We needed them because platform was too high level, not because we had not enough web APIs. If we could have a canvas and means to render efficiently, there would be no plugins necessary. And they were nightmare because you had to install them yourself on your client, not because they were not JS and DOM.