Why abandon HTML and execute Web standards?

Why abandon HTML and execute WEB standards? If it is smelly and long, try to make it as simple as possible:
HTML has three major disadvantages:
1. Too simple: it cannot meet the needs of more network devices and applications. For example, mobile phones, PDAs, and information appliances cannot directly display HTML.
2. Too large: Because HTML code is not standardized and bloated, the browser needs to be smart and large enough to correctly display HTML. Obviously, it is impossible to install IE6 on your PDA. There is not enough space, and the computation cannot keep up.
3. Mixed data and performance: to change the display of your page, you must recreate the HTML. Make different HTML for displaying the same data for different network devices.
You may say that these shortcomings do not matter to you. However, society is always improving, technology is always developing, and people always hope that work will become simpler and more efficient. However, the development of network devices will not stop due to the shortcomings of HTML. Heavy desktop computers will be replaced by more and more lightweight and small devices. Therefore, a new language is required to describe data so that all devices can understand it (XML is generated). A language is required to control performance, make the data correctly displayed on different devices (this produces XSl ).
That is to say, in the future, we will certainly use XML to convert data and use XSL to control performance. What about now?
Now, it is obvious that thousands of original HTML pages still need to work properly and cannot be discarded. In addition, the current browser cannot directly present XML documents. What can I do now even if I can?
So W3C developed XHTML again. XHTML is a bridge between HTML and XML. It is a transitional solution that guides people to gradually standardize and move towards XML. Although XHTML has "X", it cannot be extended, but it strictly follows the XML specification on the basis of HTML. It is easy to learn and has almost no new knowledge.
For XSL, we can use CSS to implement some of the functions of XSL.
The above is the answer to "why abandon HTML. It may not be comprehensive enough. The main meaning is already clear.