I agree that a better tool to add trails would be great to have. Today we can only add a point of interest and no lines to indicate the path.
But it is not an easy task to precisely draw a narrow path that is unlikely to be visible on satellite images.
You might need to use a gps tracker that is more precise than the Timeline in Google Maps.
Please know that municipalities can partner with Google Maps and then they can add such walking paths etc.
If you check the tools available to add roads you will know that it is a complex task to draw and get new roads approved.
Personally, I doubt adding more historical places to Maps is a good idea. A few people with special interests in history are likely to add a lot of such places. But is this really helpful to all the users of Google Maps? I doubt it.
Keep in mind Google is a private enterprise and they decide what they want to include and exclude from the Map.