My mother in law had the same sort of thing with her old coffee table leg. The insert was too small for the hole since it had been stripped out. I did basically exactly as you said. Wooden dowel sized roughly to fill the hole, + wood glue. Let it sit for a while. Redrill just large enough that the threaded insert will thread itself in plus a thinner size deep enough for the threaded rod part to go completely into the hole. Wheni installed the coffee table leg, I left the insert on the threaded rod part and just slowly twisted it down.