You may need to reload a page the first time after installing this addon. Double-clicking a regular image just works by itself (note that not everything that looks like a regular image on your screen will be detected as such, but the vast majority will be). The hover button also does not just show in the middle of the page in normal circumstances. but on an image. If this is your experience, you're testing it on just 1 website, and one that happens to do odd things this addon can't support with images. Please try it on other sites too before judging, or open a ticket on gitlab (or email me) and at least link me to the page so I can have a look.

Assuming the translation by google is correct: I won't build site-specific support into this tool. It's meant to be a generic image downloader that works well on sites with conventional HTML structures that expose images in an accessible way. Instagram is one of those sites with overly complicated, image-hiding webpage structures. I find a 2-star rating just for not working well on instagram a bit superficial since there's so much more to this addon and it works fine on most websites, but ok.

That's not a bad idea, though the exact format will be an issue, and you could achieve this through your file manager and a renaming program, but that's understandably more effort. Maybe I can add y/m/d h/m/s variables that you can use as desired. I'm slogging through technical work on my addons right now and don't expect to work on new features for some time still though. Please follow progress or discuss here: https://gitlab.com/Marnes/doubleclick-image-downloader/-/issues/78