If something runs horribly in WebGL, it's likely fallen back to software rendering. Device driver versions are routinely blacklisted (and occasionally entire product SKUs), I think usually for security reasons.
A given device (such as what I'm typing this on) might have an Intel integrated GPU, a discrete GPU, and depending on the system configuration run the same content at 1fps, 30fps, or 120fps.
I'm currently doing multiplayer WebGL games, and compatibility is not a very fun aspect of it.
