I’m saying this is the fault of people running badly configured mail servers. If you filter and bounce during the SMTP session instead of afterward, you won’t be emailing bounces to the forged reply-to address. Same as having an open relay. Just fix your junk if you run a mail server.

Most people these days filter while the SMTP session is still open. Reject while session is open and the actual sender gets the rejection.

Forged reply-to only works when the session is closed and you accept the email then decide to bounce it.