I am thinking about using Elm for a side project. No async backend stuff needed for now but likely at some point it will be.

This article made me dubious about investing the time to learn this language & its ecosystem.

Any thoughts?

It really can't hurt to learn a bit about it -- especially if you're new to functional programming or generally hate front-end. It also offers a good solution for SPAs and certain problem domains. It's probably easier to pick up than something in a competing space like PureScript, but it also lacks the flexibility. Elm can also be a good stepping stone to other things if it doesn't fit your style and you need more and some people seem happy just staying within the Elm realm.