Geographical relevance never seemed to be a problem with the Central, District, Jubilee, Metropolitan, Northern, or Elizabeth lines.
Most lines serve Central London, passing through various Districts of our Metropolis, including some in North London. So those names are hardly geographic or useful. But people have no problem with those.
The Jubilee was named after a single event, and the Northern Line was named after something that was never built (Northern Heights plan). There nothing on the Elizabeth line named after Elizabeth. So again not geographic and again not useful. But again, people have no problem with those.
The Overground routes did need some form of name, as it was ridiculous trying to distinguish the routes. We can all agree on that. But as soon as some underrepresented groups get a mention, suddenly it's a huge problem, despite the new names being no less geographic or relevant to the local area than most of the Underground lines? I would argue that at least they are named after something along the route of the line, so doing better than Elizabeth or Jubilee lines.
So no, I don't buy the argument about them being too difficult to understand, not geographically relevant, and not historic - unless you're also planning to rename half of the Underground lines too.