why does shopify not just use Crystal https://crystal-lang.org, it is faster than go, with Ruby like sytnax. Invidious the youtube proxy is written in it.
Because that would require porting all their code. The syntax is similar, but they're different languages (and I'm saying that as a person usually mentioning they're not that different). At their scale even updating to a new minor version of Ruby and fixing all warnings is likely a multi-day adventure. Moving to different Ruby runtime would take weeks/months. Moving to crystal would be effectively a rewrite from scratch.
Yes, "just" port ~16 years' worth of Ruby. No sweat.