Every company stopped caring, especially the companies who were at the forefront of standards and good web design practices, like Google and Apple.

Google recently retired their HTML Gmail version, mind you, it still worked on a 2008 256MO RAM Android phone with an old Firefox version and it was simply fast... of course the new JS bloated version doesn't, it just kills the browser. That's an extreme example, yet low budget Phones have 2GB of RAM, you simply cannot browser the web with these and expect reasonable performances anymore.

Mobile web sucks, an it's done on purpose, to push people to use "native" apps which makes things easier when it comes to data collection and ad display for companies such as Apple and Google.