[snarf21]

It seems like one or both things is not true. Your developers think that the tools work well enough and the system is stable enough that they don't think there is a need for arbitrary changes, meaning only you think there are issues.

Or, they don't really feel comfortable giving feedback about how to make it better. Maybe they already make such a good salary that they are afraid to risk it. In this case they are disincentivized from actually giving you the feedback.

Have you tried doing a hackathon week? No normal work except system operations but have everyone work on a new feature or streamlining of an existing process. Have you tried offering bonus for people who offer up new ideas and plans to improve the software and processes?