In SLP 404, bitcoin maintainer, Gloria Zhao says more than 70% of bitcoin development work is maintanance work, not stuff like Taproot.

"**And so even if nobody was opening pull requests to request new features or point out things to Bitcoin Core, you would still have the job of finding bugs, fixing bugs, monitoring things upstream, updating dependencies, making sure we support things continuously downstream, cutting releases — to do that on a regular cadence, taking care of what happens on the GitHub repository** — responding to issues and triaging pull requests and all those things, running CI — testing things. And so every software project requires maintenance."