Well, the perfect downloader that you were looking for is JDownloader. It is open-source, can download from multiple links from a file into a single folder automatically and intercept browser downloads (with an extension). I've never used a premium file sharing host, but JDownloader does have options to log in to your account on many hosts, so that if you have a premium account on one of them, you can get the higher download speeds or bypass any bandwidth limits by the host, etc... I'm not sure about downloading YouTube videos though, I don't think JDownloader has a built in way to download YouTube videos (correct me if I'm wrong).
Piracy
Welcome to /c/piracy
No netflix or streaming services landlubbers allowed, this is pirates territory.
It does. If you paste a YouTube link, it asks to install FFMpeg, and downloads the video. You can also download audio.
Oh that's nice, I didn't know that
This in combination of free download manager to get download links has help me download large video files from cloud link/browser download
JDownloader is partially closed-source.
Didn't know about that, what parts of it are closed source?
Various plugins, see https://board.jdownloader.org/showthread.php?p=517795
However, it is possible to use JDownloader without these.
Motrix. You can even get an extension for your browser to automatically add downloads to Motrix.
Free Download Manager (FMD). FOSS
Xdman. It is opensource and can download directly from firefox/chrome
I have tried a lot and always go back to Jdownloader. Nothing really compares IMO
Gabut DM check it out.