I can right-click and save videos just fine. You can too, try it here: https://thumbs.gfycat.com/GregariousDevotedArachnid-mobile.m...

You just have to write some Greasemonkey script to circumvent all the crap that the video-serving websites do to prevent you from getting the normal video-in-a-browser UI. It's harder when you get this link https://gfycat.com/GregariousDevotedArachnid