Sounds like the same issue I had till I figured it out: You got an iPhone/Apple? if so there is a “choose image size” option at the bottom of the dialogue AFTER you check/select the photo
..emphasis on AFTER
I couldn't find a way to reduce the quality of the pictures on android, what I do is take a screen capture of the photo displayed on my phone and upload it. Its a much smaller size picture but still displays fine on forums or when sharing pics by email.