Just taking this moment to share something I made from a similar point of frustration — https://mood.site
It's a free online photo gallery app where auth is done through URL query params. You make a board, it gets an edit key, and then if you share that url with anyone else (including grandma) they can upload photos without needing to make an account. You can drag and drop, use the upload button, and it works on mobile as well.
There are lots of other little features as well, but the core thing is just a dead simple (online) photo gallery tool. You can see some sample boards here:
Know that URLs are not secrets. If they're not seen along the way, they're generally sent to safe browsing checks etc. and one way or another quickly become part of the crawl.