Rails is attempting to solve this with Solid Queue, which was inspired heavily by GoodJob, both of which use Postgresql (and more in the case of Solid Queue). Both seem to be fairly capable of "serious scale", at least being equivalent to Sidekiq.
I like the sidekiq guy and wish him the best, but for me, the ubiquitous Redis dependency on my Rails apps is forever gone. Unless I actually need a KV store, but even for that, I can get away with PG and not know the difference.
Unfortunately there are still some CTOs out there that haven’t updated their knowledge are are still partying like it’s 2015.