> Instead, it's all either slow, slow backend frameworks like Ruby, or even
Usually this is a matter of bad coding or overprovisioning of whatever is being used to host the site and the DB. Most maintained languages running on modern hardware can sustain reasonable loads without any significant performance issues. While client-side bad-performing frameworks abound, the last I looked into it, Ruby+Rails isn't that much worse or better than any other.
It depends heavily on what you are doing.
Most CPU intensive Tasks are fast on everything. However on Memory intensive Applications Ruby and Python are really really aweful slow.
Usually this is a matter of bad coding or overprovisioning of whatever is being used to host the site and the DB. Most maintained languages running on modern hardware can sustain reasonable loads without any significant performance issues. While client-side bad-performing frameworks abound, the last I looked into it, Ruby+Rails isn't that much worse or better than any other.