Legacy code. Language, ecosystem, frameworks, libraries, from 5~10 years ago that people should have moved on from, but due to their lingering popularity we can

Legacy code. Language, ecosystem, frameworks, libraries, from 5~10 years ago that people should have moved on from, but due to their lingering popularity we cannot get rid of. It sucks signficant communal/company effort to maintain and friction to develop - so much so that there's not enough energy left to actually migrate to newer and better solutions. The only way out is a multi-year vision of gradual migration, replacing part by part, keeping backward compatibility as much as possible. Fortunately, some smaller projects or green-field ones can be started on a new foundation. But it can be discouraging to see how slow the progress is, and feels like it's dragging down the devs' own career progress too.