I do not agree that it "has completely different semantics". It has far more in common than not. Its close enough that I, as a long time Ruby developer, had no issues being productive with it in a very short amount of time. The syntax and API are similar enough that most Rubyists are going to be very happy and comfortable. Then when they see the benchmarks they will be even happier!

It also has different semantics for bad reasons. For example, Ruby’s if ... then ... else (single-line) has been deliberately removed because the devs have a mild preference against it. For someone like me who’s been writing that since BASIC in 1981 or so, that’s a surprisingly big PITA.

I like Crystal, but there are a few too many needless gotchas for it to be comfortable.