I used to use HTTrack, but then I found Cryotek WebCopy[1]. It's basically same, but with more user friendly GUI and some more features useful for modern web. Like for example, it can fetch resources by URLs contained in JS code or from special attributes like data-src. And it's free, but available only for Windows, though.

[1] https://www.cyotek.com/cyotek-webcopy