You are too optimistic. The js mind virus is spreading inside fast. The old devs' moving up, the new naive devs' moving in. Web tech is heading towards what tech influencers and companies making money of. You will never see shiny VC backed companies pumping Rust outside of the bubbles.
They clearly haven’t read the HN comments about Ruby
I am not aware of any HN comments that point to Ruby ( or Rails ) being a bottleneck.
Most of them only suggest Ruby ( or specifically Rails ) being more expensive to scale.