Past failure does not inherently prove future failure. Plenty of things were implemented poorly and yet people who favor them will argue that it just needs to be done better.

Are they correct or are they missing something core enough to the issue that makes poor implementation and almost assured outcome?

And for bans in general, there are many bans that went poorly yet people still generally approve of a ban, even when it has unintended costs, as long as they have a strong dislike of the item being banned.

For example, CSA image bans have a history of being used to restrict freedom (such as the recent attack on encryption) and great personal cost to individuals (any kids who get caught up in laws that didn't make exceptions for kids committing the criminal acts), and they can largely be judged as a failure (from police and news reports of how the problem continues to grow worse). Yet such laws have extremely widespread support, more than most any other law I can think of, to the extent where even reasonable rollbacks of the existing to attempt to fix some of the current problems can kill a political career.