Yes, but this is the nature of the Web. The limits we're discussing are real on many devices, which means content won't work if it exceeds those limits. Outside WebGL, it could be that some devices don't support 1080p video, or complex Web Audio graphs, or run out of memory with a huge HTML document.
A great feature of WebGL is that it exposes API to detect those limits. Most other Web things don't.
I think another reason this has become a point of concern is that iOS updates are more available to older hardware than other systems. We could have decided to not enable WebGL on older devices, but that would be a huge shame - the devices are capable, just not as powerful as desktop machines. There is no shortage of GLES2 native apps that run on them.