After the initial round of "useful PyPI packages don't support Python 3 though, I can't migrate", that "I know 3.x is different and I'll have to read up on the

After the initial round of "useful PyPI packages don't support Python 3 though, I can't migrate", that "I know 3.x is different and I'll have to read up on the differences....later" was absolutely the biggest blocker for adoption imo. I know proficient Python programmers who were starting projects from scratch in 2017 and didn't want to use Python 3.x because they were in a hurry, worried that they didn't know how to write Python 3.x in a timely manner because they hadn't invested the time to learn it. Lots and lots of people just knew it was a known unknown for them, had no idea of the magnitude of the effort required to switch (tiny for new projects! tiiiny) and just put "look into this" somewhere deep on their backlog.