Elon stated this multiple times and yes, a fully autonomous system needs to be capable to detect lanes in absence of map data or when the map is wrong. Still, map data can be beneficial. It's the silicon equivalent of long term memory. Same as a human driver with local knowledge, the car select the best lane far ahead and when visual cues are poor (e.g. snow cover, degraded markings, other cars covering, ...), which would impact even a superhuman vision stack.
From various reports, I gather that older versions of FSD were giving more weight to map data or perhaps lane-level map data is currently ignored entirely. To me, Tesla should seek to improve the map data, at least in a certain reference area. They should bring it to a level where it's almost always correct like 99.9%. Given that there already is a feedback channel, this would not take a lot of effort, especially if done for a limited region only. That would not only improve the user experience but also make it easier to detect cases where FSD gets it wrong.
The Mobileye-based Autopilot was first introduced in October 2014. Tesla started from scratch in July 2016 after the breakup from Mobileye. What we're experiencing today is the outcome of 6 years R&D at Tesla. According to wikipedia, the FSD Beta started in October 2020.
Is your experience so bad that it feels only like 20% done?