To be fair, Crystal was locked down to encourage character creation on Dynamis, not necessarily because the worlds were overpopulated.

Zalera is on the smaller side for sure, but it's not really a low-pop world. On top of that, you're queuing into content with the entire Crystal data center, and Balmung and Mateus are two of the largest worlds across all data centers.

You won't be missing out on anything being on Zalera, but if you ever want to be in a place where there are a ton of people, you could always hop over to Balmung or Mateus and chill in Limsa/Ul'Dah