I've scheduled a request from report builder to be sent to an FTP on a daily basis, however, i would like that the new file overwrites the existing one but this is not the case and it's creating a new file every day (e.g "filename (1).csv", "filename (1) - copy.csv", etc.)
The thought process is that the report builder files are mostly for human consumption and so files don't get overwritten and lost.
Similarly, the Data Warehouse tool overwrites the files, since these files are commonly fed into a system and need to have a static or a certain pattern of name for the files.
If you are using the Report Builder for dashboarding, you will need to continue as it is. If the file you are generating is for feeding into a system, you can check whether Data Warehouse resolves your issue.