The sky is not falling and placing a shunt in the starting circuit is not "bad practice."
There are thousands of high current DC shunts installed in motor and other power circuits onboard ships where the current flow far exceeds a tiny engine starter.
What is it about a shunt that freaks you out so much? Why is it so much more dangerous than a cable terminal or - gasp - a battery terminal?
This is the kind of myth and "sea story" nonsense that make small boat mechanics and electricians rich ... people read utter nonsense on boating forums and actually believe it even though the people who post the garbage can't support their position with anything more than rumors and their "net creds."
I challenge you to show us why a shunt installed correctly with clean terminals that are properly tightened is any more likely than any other electrical component to fail and cause the sky to fall.