Ad fraud is a political problem, not a technical or resource problem.
In the political dimension, the issue could be addressed by taking advertising away from the people as a service that is generally providable and restricting the right to advertise online to a few elite who have been vetted.
The power of advertising (as in buying influence) should absolutely require vetting and approvals. This is already done today, and comes in many layers as scale and budgets increase. The problem is profits that do not incentivize stopping these ads effectively.