One of the authors of the paper has said "WAFs are just speed bump to a determined attacker."
One of the authors of the paper has said "WAFs are just speed bump to a determined attacker."
This isn't like having a lock on your door, this is like having a cheap, easily pickable padlock on your bank vault. If the vault has a proper lock then the padlock serves no purpose, and if it doesn't then you're screwed regardless.
WAFs can have thousands of rules ranging from basic to the sophisticated, not unlike mechanisms you can deploy at a checkpoint.
Security devices like IDSes or WAFs allow deploying filtering logic without touching an app directly, which can be hard/slow across team boundaries. They can allow retroactive analysis and flagging to a central log analysis team. Being able to investigate whether an adversary came through your door after the fact is powerful, you might even be able to detect a breach if you can filter through enough alerts.
People are more likely to get dismissed for not installing an IDS or WAF than having one. Its effectiveness is orthogonal to the politics of its existence, most of the time.