I was forced to encounter Web2Py in an open-source project several years ago. It was awful. Besides the fact that it's stuck in Python 2 (seriously, even today?), it had a lot of bizarre design decisions. For instance, it loaded controllers by concatenating files in a directory - alphabetically. I know Python's import system can confuse some folks, but surely there was a better way. The whole thing left a very sour taste in my mouth, so I rewrote the application in Flask - unfortunately, the lead developers didn't seem interested in my fork. I've moved far away from their project, but I'm not sure what they're going to do come 2020.