Ruby is something like a "improved" Python, with a better OO system, a code block syntax that makes it easy to use callbacks, more consistent standard libraries, etc. It could be what Python is today.
I wouldn't say niche, but the killer app of Ruby is Rails, a web framework similar to Django. In fact, many people treat them as they are the same. But there are big projects that use Ruby and that are not related to Rails. As far as I remember: Metasploit, Homebrew, Vagrant and Jekyll.
Personally I think Ruby is amazing language for writing shell scripts. I write a blog post about it, you can see it and its discussion here: https://news.ycombinator.com/item?id=40763640
Can you name one way Ruby has parity with Python? Ruby is a dead language that uses sponsored posts here. Nobody actually uses this since like 2018 but some people are paid to hype it up. Just look at the empty praise. No real applications mentioned.
It's not just the well-known GitHub, Shopify, Chime, Figma, Zendesk, Convertkit (Kit), Coinbase etc.
See the "few" companies here, actively hiring Rubyists for no reason https://rubyonremote.com/remote-companies/
Square, Gitlab, Cisco, Figma, Instacart, Block, Calendly, 1password, and so on
I wouldn't say niche, but the killer app of Ruby is Rails, a web framework similar to Django. In fact, many people treat them as they are the same. But there are big projects that use Ruby and that are not related to Rails. As far as I remember: Metasploit, Homebrew, Vagrant and Jekyll.
Personally I think Ruby is amazing language for writing shell scripts. I write a blog post about it, you can see it and its discussion here: https://news.ycombinator.com/item?id=40763640