I've repaired a number of antique doors through the years. Just got done with one over 100 years old last year. The dowels are big, 1/2" diameter and about 8" long. They go deep into the rails and stiles of a door,and are usually spaced about 2"-3" apart. I've never repaired a broken dowel, or had them come out easily. They almost always broke/split the wood on the face of the stile.
Dowels are like any other joinery technique. They have their applications. They do require a significant effort to maintain symmetry and uniformity of a joint, or it won't go together. Antique doweling machines, when you can find them, are still very expensive.
They will not equal the strength of a properly sized and fitted M&T joint, but they will be stronger than the two pieces of material they are joining together, if sized properly.
"The first thing you need to know, will likely be the last thing you learn." (Unknown)