My old Android Galaxy S10 lets me resize photos before I post them. I try and keep my photos to web-friendly file sizes of 1/4 Gb or less, aka 250k. On my phone that usually means crop, then shrink to 20% or 40% of original size. I usually post from the computer though, so I use GIMP to crop and resize before I post.
@Son of Hobbes was gonna work on a server-side solution to reduce file sizes.