It isn't broken. As far as standards go it is a fairly clean and easy to implement one. (That is the reason for its enduring popularity.) Source: wrote a term

It isn't broken. As far as standards go it is a fairly clean and easy to implement one. (That is the reason for its enduring popularity.) Source: wrote a terminal emulator once. Turned out to be not that difficult. We just need to agree on an xterm-compatible subset of functionality and throw away the rest, which nobody ever uses anyways. Your complaints are just aesthetic complaints, the terminal isn't supposed to be a universal GUI toolkit.