mate, I've run enough audits on dental clinic accounts to know that Demand Gen can work, but it's rarely the right starting point. your agency keeps pushing it because it's a high-cost, low-control format that makes their reporting look pretty - lots of impressions, light on actual leads.
Here's the problem: Demand Gen targets Discovery and YouTube feeds, which are great for brand awareness, useless for getting someone to book a cleaning. For a dental clinic you want Search ads and Local Service Ads - intent-based stuff. someone types "dentist near me", you want to be there. Demand Gen shows your video to people watching dog grooming compilations.
If your agency has been pitching it several times without proving it works for your practice, that's a red flag. Ask them for the conversion tracking data - cost per lead, lead to patient rate. If they can't show you that, demand a switch to Search + Local Services.