Or even more precisely, the VM of its main (and de facto default) implementation needs love. Rubinius and JRuby are really VASTLY superior implementations but well, there's no specification so 50% of development time is spent in asinine catch up with an underspecified "standard" (MRI that is).
Really sad state of affairs and the #1 reason why Ruby isn't faster and more feature-packed.
Really sad state of affairs and the #1 reason why Ruby isn't faster and more feature-packed.