Many URLs from my site have been added to Google's index, but a lot of them are outdated and they will never result in a
404 error and take the user to my site's homepage.
I have submitted a new sitemap with my latest URLs, but the the old and obsolete URLs of my site are still shown on top in Google search. There're 100's of such URLs.
I know about creating URL removal requests and robot.txt. But submitting removal requests will take a lot of time and effort. I would like to use robots.txt instead. But if I list them in my robots.txt using a wild card expression that matches my old URLs, will Google remove them from its index? Or will it just stop crawling them again, which means they will not be re-indexed, but already indexed old URLs will still be shown in Google search, which is not I want. Can you please let me know what I should do?