Would you also suggest people not use frameworks, since using the core language is what they are supposed to be doing?

Additionally, I guess an ORM or query builder of any sort isn't worth it either.

I suspect for a large percentage of sites JS on the client may be faster than the language the site was implemented in (even at a pure language level, ignoring that you offload computing very efficiently).

Why is using abstractions that we all (well, many, if not most) believe to be of benefit on the server any different when run on the client, especially when it's more efficient (compared to server) and scales better?

Sure, if someone thinks they have a need for raw javascript performance but they haven't tested and confirmed this, maybe blind assumption isn't the best way to proceed.