I've used Koa in my last few work projects but will be either switching back to Express or moving onto Fastify for the next one. Like you mentioned, Koa does indeed feel dated. It's community never really took off, either; many of it's most popular helper/companion libraries haven't been updated in years.
I still use Koa out of habit since it was the only framework for a while that had first-class promise support.
One thing nice about Koa is that it's simple, so it's timeless in that way—it's not a moving target nor does it try to do something that needs a lot of core maintainers.
