There are workarounds. One is using a free iOS file manager app like Documents by Readdle. Use the Safari browser to visit a YouTube video, and use the Share option to find Copy Link. Then go back to Documents, and use the built-in browser in the app to surf to a video download helper site like SaveFrom.net. Paste the link into the form (hold your finger down on it until you get "Paste" menu to pop up). The site will give you the links to download, and you can save the file to Documents. Hold down and drag the file up, until you're back on the main screen, then drag it to the Photos folder. You'll need to give Documents permission to access Photos the first time. You can then access the video like you would any video taken on the phone or tablet—in the Photos app.
List the video as Private: When you’ve uploaded the video listing the video as private, only users you’ve shared the video with can access your video. The video uploader has to add each authorized user manually for each video. However once permission is granted, the user can download the video using youtube-dl (either through terminal on Linux or through their .exe program on Windows)
However, even free, you can grab 4K video from YouTube with no problem. A 575.4MB file took over 10.5 minutes—no surprise with the speed restriction, but still agonizingly painful. There's an option to convert the file to MKV, AVI, or WMV as you download it. If you want a playlist, you can do them in a batch, but in my test TubeGet would only allow a max of 1080p HD even on the 8K video playlist.
The DVDVideoSoft system gives you free downloads in just about any style you might need. It’s an easier YouTube video downloader that consists of only three different steps. The system is older than some because it’s more than ten years old and it provides some of the best quality you could want. It’s available to be used on both PC and Mac computers, which gives you the level of versatility and flexibility that you’re looking for before you even get started. Plus, you can get a range of different options or different formatting features to the videos that you want to download.
Not to be confused with the unrelated "pro" above, Video DownloadHelper supports a huge number of sites—even those for adults. You'll know a video is downloadable when the icon for the extension animates when you're on the webpage. Video DownloadHelper for Chrome has stopped working with YouTube—so it could get placement in the Chrome Web Store. You can get around that by using the Video DownloadHelper extension for Firefox. The developer has a Kiva initiative page, where it prefers you donate funds to those in need, which has raised over $137,700.
You never know what’s going to be pulled down from your favorite social media sites. That means, if the show is removed, you wouldn’t have any way to access it. If you’ve already downloaded that information, however, you’ll be able to pull it back up and watch it over and over again, however frequently you want. You don’t have to worry about whether it’s going to still be available on the social media site you use when you go back to it.