My biggest complain about SO is that with the expansion into other fields that questions that used to be welcome on SO (or get more visibility because of being on SO) are being shunted to SuperUser or ServerFault or other sites under the StackExchange umbrella. [1] I think the drive to keep SO purely about "programming" runs into issues similar to the "No True Scotsman" fallacy [2]. As a developer, sometimes I need answers about Amazon Web Services, Azure, Docker, or the Linux command line, as a consequence of programming, but those sorts of questions are, more modernly, marked off-topic for SO.
1: https://stackexchange.com/sites 2: https://en.wikipedia.org/wiki/No_true_Scotsman