So why the applause from the developer community ? A good question and the answer, bar that it comes from Google, is that assuming you can truly appreciate OOP and Google use C++, Java and Python, you are building a real application here which will, in time, take the web to the next level.
For run of the mill sites, A2 is probably a bit too complex, but if your site is more like an application then A2 would be the way to go. We are currently writing some CMS in A2.
Any A2 web-site will in effect be a complete re-write and you really have to use A2 as an IDE. In fact you don't really need other libraries with A2 [such as react or even jQuery].