You could if you wanted to do so. However we cannot encourage a beta to be used on a production site, and you may well wait for fixes or even have to revert at times.
Sorry to hear you a discouraged. Of course we will never please everyone, all of the time. Its worth noting live community features are available on 4 also, but not on a self hosted environment. Quite simply, they require cloud functionality to work.
This has already been done.
We have said we are looking to bring tables at some point. Other items have been discussed at length already, but in short, the editor is more functional for most people. The items you mention there, are, for the most part, items that should only really available to advanced users. As a developer yourself, you could actually add your own applications for items such as these if you wanted to do so.
Conversely, we have also talked to many customers, who cannot wait for version 5. In fact, we have actively had to encourage some not to upgrade their sites too early, as its still in beta. As mentioned above, we will not please 100% of people, 100% of the time. As you have already seen straight after your response, not everyone agreed with your sentiments there.
Yes, HTML is indeed not possible to add within the editor. I would however encourage you to explore other ways of working, and ask if similar things can be achieved in a different manner. Using your example there. What exactly are you using that code for there?