What do you guys do when you get stuck behind a car going half the speed limit on twisties?

I was riding out in the twisties today and got stuck behind an old person in a Toyota Corolla. The posted speed limit was 80km/hr, they were sitting at around 40 most of the time. There was a 10+ car queue including me behind them. Single in broken white line so no overtaking unfortunately.

I ended up pulling in to a rest area and waiting 20 minutes. I tried riding safely but also in a way that made it clear I would like to go past to no avail. There were multiple bays literally labelled for slow cars to pull over. Are better ways to approach this?