I'm biased (I created programming.dev), but I think lemmyrs.org should definitely not be the main site, but that goes for any site with "lemmy" in the name. The entire purpose of federation is that the software doesn't matter. If things go south with lemmy in the future, or people fork it, or just want to migrate to different software you've now completely tied the identity of the site to the software it's running on, which just really seems dumb to me. The reason I chose programming.dev as the name is several reasons.

• It immediately tells you what the website is about
• It's easily remembered.
• It's indicative of what you will find on the website, not just one programming language, but all things programming at all.
• It's one general concept.
  • It's not extremely specific, which contributes to website 'rot' as only specific users of that specific community will ever use that site. It promotes growth, as almost anyone can find a home on the website. It encourages branching out into different topics, as you might come for Rust, but then find the Kotlin community and think "what's that" and go learn something new.
  • It's not extremely general. For the majority of lemmy sites, you have no clue what kind of communities the site hosts, so you have no reason to choose that instance over any others. For example, lemmy.world, what is it about? What communities are there? Why would I choose lemmy.world over lemmy.ml over shitjustworks (where even do you put the dots there? That has to be the worst named site out of all of them really).
  • There's either no opportunity for growth if you go too specific, or too much opportunity for growth, completely defeating the purpose of federation if you go too general. "Programming" as a concept is plenty large, while not encapsulating the entire world.

Of course, these are my own opinions, but I did think for a long time about it before settling on the website name, while it seems most server owners did not really think at all about their site names.