It's the same situation in London, only about 25% of Underground stations are accessible[1]. This seems to be the cost of old infrastructure - when most of the network was built, accessibility simply wasn't a consideration. Neither was having a decent mobile signal, or air conditioning. Fortunately, we've learned from this and newer systems like the ones in Shanghai and Taiwan seem to be far more accessible.
Progress is being made, however. Stations are currently being retrofitted for step-free acccess at the rate of around 30 stations every 5 years.
OK, it'll be many decades before every station is fully accessible at that rate. But progress is being made. The Tube is infrastructure which will likely still be around for decades or centuries to come, so it's worth doing.
TfL's online status tools and journey planner are also pretty good at keeping track of any lift outages, etc, so it's unlikely anyone will turn up to a station to find a broken lift unexpectedly.
For mobile signal, TfL wanted more money and better cooperation than the mobile networks were willing to provide.
The speed of the upgrade programme was reduced by Johnstone, but is progressing. The three disabled people I know, have organized most of their lives around the parts that have already been upgraded or other transport methods (DLR, trams in Croydon) but still very much appreciate the improvements as they are made to the Underground.
[1] https://tfl.gov.uk/transport-accessibility/wheelchair-access...