People always say Ruby is dead, but there are quite a few companies are (partly / fully) using Ruby (and Ruby on Rails):
Archive Of Our Own
Forem (Formerly DEV)
As of 2020.03.08.
See also: Top Ruby Companies.
Ruby on Rails is no. 3 (1.45%) in Programming Language Usage Distribution in the Top 1 Million Sites
Ruby on Rails is no. 3 (4.17%) in Programming Language Usage Distribution in the Top 100k Sites
Ruby on Rails is no. 3 (6.63%) in Programming Language Usage Distribution in the Top 10k Sites
Web Framework by Wappalyzer Ruby on Rails is 9.5%.
Many people using it does not mean you should or it’s the best choice. But it shows that Ruby does work for them and you could spend more effort to explore with Ruby.
I think the biggest reason people choose it is because it is productive, especially in the early days of your business.
Ruby is definitely fast enough to get your ideas out to the world.