I agree the screenshot upload process isn't the best, but we're doing what we can. It's something we can certainly revisit at some point.
As Beardgoblin mentioned, I personally prefer uploading to imgur (if anything, for the image compression) and then posting to the thread via bbcode.
In the early days of the site, we were getting people uploading insanely large raw images which actually "broke" my initial attempt to test out a new forum system since we couldn't migrate. I'm looking into upgrades for our current forum, and I'll be sure to include more efficient screenshot uploads into that investigation.
Thanks for the feedback.