So it sounds like you should be looking for a better career opportunity. In order to make that a natural progression from your current employer I suggest getting to know the product folks, UX people, actual users, or whoever knows, so that you can get a sense of what future or long-term needs are for the system. You aren't after a specific task list but rather a general direction. You can then start looking through the parts of the codebase that are closest to that direction and considering ways of adapting them to the new direction. In the process of doing that you should identify which technical skills/languages/technologies are the best fit and in the highest demand (at other companies) and closest to your current skillset. If it is an open-source piece of tech then engage with the core contributors on that team, subscribe to their mailing lists, and learn from that team rather than your employer. It is better to learn from multiple individuals than from a single mentor.