>People keep complaining about how slow Atom is, how much memory it hogs up, etc
Which is exactly what people have been saying decades ago about Emacs, aka "Eight Megabytes And Constantly Swapping".
The difference being that, functionality-wise, you don't get anything from using Atom over, say, Emacs or Vim. High memory and CPU utilization is a tradeoff I'm willing to take for the added benefit of running IntelliJ or Visual Studio, because as environments they do way more for certain code bases than either Vim or Emacs could do. But Atom? Not so much. "It's made of Javascript and HTML" is not an advantage (to me) worth the memory and lag.
You're right on run anywhere with a terminal and high quality packages. However, Atom is truly extensible in any way you want because it's actually made up of lots of packages that you can replace and fork.
(I'm a Vim user myself, but I feel like comparing Atom to Emacs is a big... optimistic. People keep complaining about how slow Atom is, how much memory it hogs up, etc. I think it needs at least a few more years of maturation before being able to call it "the Emacs of X")