Why not?
1. it's not compiled and evaluated at runtime, which make it harder to test. Pesky undefined variables in edge case code.. 2. deployment is tough when it's a ton of small files. Most things compile to a single executable binary 3. it's not concurrent or parallel easily. You're not going to easily use all your cores and also develop sane software.
For example, Github, Shopify, and Hulu were written with Ruby on Rails and they seem to do alright.
Some of the work on Ruby and Rails that Shopify and Github have produced is available to the community as well.
For instance: https://github.blog/2022-08-25-introducing-trilogy-a-new-dat...
Facebook heavily use, or did use, PHP dont they?
IIRC the Threads backend is Python as well. Which seems to be doing OK!
Difficulties using all your cores with Ruby was a problem when I first started using it 18 years ago. It hasn't really been a problem for things like web serving for the last ~15 or so.