This, but also I like to at least have a Hello World console app (or API server or web page or database reader or whatever the bare minimum is) that I can play around with and know that I can create something from scratch and not be entirely at the mercy of whatever the work infrastructure is.
But I also agree with the last sentence. When you are just starting out in your career, it's nice to have something more complex (I used to write sudoku solvers) to really get the feel of things. I'd never do that anymore though, as most things are similar enough to something I'm already pretty comfortable with.
The default used to be a blog engine. It's a complex enough web app that you can learn how web servers and database access work in the language/framework. But it's also easy enough that you don't need to spend a lot of time on a data model.
The benefit is that the design of a blog web app is going to be very similar in a variety of languages that you can compare different frameworks/languages pretty easily. The downside is that if your language is better at non-webapp things, it's not going to be an easy exercise.
But I also agree with the last sentence. When you are just starting out in your career, it's nice to have something more complex (I used to write sudoku solvers) to really get the feel of things. I'd never do that anymore though, as most things are similar enough to something I'm already pretty comfortable with.