And yes, I was wrong, rails has been around longer than that, it was just a guess.
The reason I've been teaching it myself, despite Elixir being a young, niche language is that I believe it's an ideal choice for a solo-founder or small team trying to build an ambitious web app. It's a tool I personally want to have at my disposal.
Discord is a great model: start with a simple Phoenix app, ship way faster than the competition, build out more sophisticated infrastructure with scale, and then finally rewrite core loops as NIFs (natively invoked functions) that are implemented in Rust. They were in a crowded market with extremely well-funded competitors and they still built a considerable lead in product and infrastructure.
I am saying it does not matter if they are sufficient on their own. If you want to find professional work as a frontend dev in 2021 you will be expected to learn larger and more complex toolchains.
I am sure there are plenty of applications in maintenance mode using simpler tech (or possibly not, because the lower complexity means that there are far less bugs?)
For frontend it's no longer enough to know HTML, CSS, basic JavaScript and maybe JQuery. It's not enough to render static templates on the server. You have to build a SPA with dynamic bindings and a build pipeline with webpack or whatever else.
It's all just ballooned like crazy and personally I found it incredibly hard to keep up with all of it. So I'm trying to transition into either front or back end, so I'm not trying to learn full stack everything anymore.