Hey, thanks for the thread! We're glad that you've brought up these concerns with us :]
Currently, our developer team works on so many different avenues of the server at one time - from protocol versioning, to anticheat, to game updates, we have a lot of code pushing to our server every day. Inevitably, bugs will appear as a result.
It's a shame to see a load of bugs go by, I do agree with you on that. And since we're always wanting the best player experience you can get in Minecraft, it's unfortunate that you feel like we haven't upheld that, and for that, we apologise.
We've realised for a while that bugs aren't being dealt with any sense of urgency, and we're currently reworking internally how to deal with bugs without a great delay. This includes a more structured way of dealing with network bugs from a development standpoint, as well as getting more people involved in reporting these bugs (e.g. when they're reported in staff-help with a /whereami output - this is often extremely important in fixing a bug) and assigning priorities.
The suggestion itself though, which is to fix games before adding new ones, is unfortunately not feasible. We're in a privileged position that we're able to develop and experiment with awesome features outside of what you think is possible in Minecraft, with our extremely talented developers, and we cannot wait to show this off to you! However, we will hopefully develop and work on our internal systems so that we're in constant rotations in fixing bugs, as well as providing new content for everyone to enjoy. I would love to have a wider conversation about the state of bugs after we've spent time changing the current method of dealing with bugs.