why hasn’t China fixed it in the over 25 years?

Because when China under Deng took it back from Britain by basically telling them “fuck off or we’ll do it by force” and Thatcher agreed (knowing full well they could not fight to keep it and would have had very little support for that anyway other than the western shitholes which were more concerned about the USSR and other communist countries in europe than China at the time), one of the requirements of the deal that Britain made was to keep the current system with unchanged policies for 50 years. This was signed in the Joint Declaration.

This blueprint would be elaborated on in the Hong Kong Basic Law (the post-handover regional constitution) and the central government’s policies for the territory were to remain unchanged for a period of at least 50 years after 1997.

So if you want to complaint to the correct people responsible the way it is currently, complain to the British.