Don't worry, development on Query Monitor isn't stopping and the plugin isn't going anywhere.
In order to work on some larger changes to Query Monitor (primarily switching to client-side rendering) I need to put a pause on regular feature development and non-critical bug fixes. I anticipate this pause to remain in place through spring 2024. This will allow me to focus on the bigger changes that I need to make.
Feel free to continue opening issues and PRs. I'll get to them in due course, just not right now.