I switched from Express to Koa for a few months now and I honestly don’t understand why this doesn’t seem to be the trend. It was a simple transition but everything feels more correct to me, and easier to reason about.
40 nodes, with one being an "unspecified" license. That's a reason not to switch.
For one, people pick from number of github stars which is about 40k vs 20k and when you google for node web framework, Express is of course on the first page and Koa is not and for those who read blogs and books from only a few years back, they all talk about Express.
'basic works'.
Especially if it's familiar.