The bar for entry for any of these solutions is

1) require no app installs (at least beyond those you already have).

2) not require the same network

Most solutions fail one or both of these. Of course AirDrop isn't perfect (It doesn't work outside iOS so if you know any Android users you are quickly out of luck).

I made websend to make it easier and secure to send images from phones to computers. It also allows automatically OCRing and cropping etc to turn a bunch of pictures into a proper pdf when there's no flatbed scanner around.

https://github.com/thiswillbeyourgithub/WebSend

Note that I'm currently refactoring it heavily (the code is awful currently).