For the WSL part: that's one command in powershell/cmd and then a download from the Microsoft store. You won't find it challenging, there's not much more to it than that in 99% of cases (and if you do run into issues, there are probably better alternatives to trying to fix WSL anyway).

As for C++, Ladybird uses very modern C++ that makes it substantially easier to write reasonably safe code than the C++ of yore.

Still, as much as I would like to see the world move to safer languages, C++ is everywhere. Every major browser is written in it. It's not "unusable" in the slightest (though I certainly understand not wanting to learn C++ as an outsider at this point in time, it's a quite boring language in comparison and the C++ job market probably won't let you make use of modern language features that might make it interesting).

I would love to live in a world where projects with security risks like web browsers would "just" use Rust instead of C++ but you'll have to convince the people building the browser to spend their own time or their bosses' time to learn Rust first, and that's a tough sell.

There's Servo if you want to contribute to an open source browser in Rust. It looks like it can certainly use the help it you compare its development speed with Ladybird.