Even with Firefox's screenshot feature, it's still a worthwhile extension with features/options the Firefox screenshot does not have; with the extension you can do simple things like make notes, blur, circle parts(circle or square), highlight, and crop without the need to open an external app. And you can quickly copy the image to clipboard instead of saving if you need to do a bit more advanced editing in an app.

But the crop feature can freeze up with large areas, and the blur tool only has 1 brush size, so blurring can take long. If you need to blur something, I recommend just copying the screenshot to the clipboard and blurring it in Photopea.