Listing every team folder and date last modified

As you found, starting from files_list_folder(path='') will only list the contents of that particular member's folder; if there are other team folders that the member doesn't have mounted in their account, those team folders won't be found that way.

You can list all team folders for a team using team_team_folder_list/team_team_folder_list_continue though. (Similarly, if you want to list all "namespaces", which includes team folders, you can use team_namespaces_list/team_namespaces_list_continue.) These methods are called using a DropboxTeam instance, not a Dropbox instance, so you would call them without the 'as_admin'.

Then, you can start listing any arbitrary team folder like this:

dbx_team.as_admin(admin_id).files_list_folder("ns:" + team_folder_id)

And for reference, if you need to list a "team space", refer to the Team Files Guide.