Indeed, people need to stop fretting about “the cgi is only 2k.”
With few exceptions, that’s still how it’s done today even when the movie is finished as a 4k DI. It’s simply more money than the studios are willing to spend to render it in 4k, especially when it’s a very vfx-heavy movie.
Going forward, 4k rendering will probably become more the norm as technology improves and costs come down.
Do we know what res the cg in TFA and RO was rendered at?