Depending on how it was implemented, that could just increase the attack surface. Assuming it's a cloud service, now we have another company that has all your passwords, that can be breached. A better way would be desktop software that runs on your local machine and logs in to each web site by itself and changes all your passwords, without using any remote compute or storage, outputting a local file with all your new passwords (don't make the same mistake again using a cloud password manager).