I exported my LastPass vault (yeah I used to be on LastPass...) and imported it into Bitwarden. Maybe I was lucky, but I was amazed by how simple it was. It took like 2 minutes, and it just worked.
Unless you also changed every password for every account you store in your password manager, you still have the original security issues of Lastpass to deal with, as well as any potential issues from your new password manager.