I do feel that IOT would benefit from being longer - it often feels rushed. Podcasts excel at "deep dives" in a way that radio is barred from doing: a podcaster can say "I think I'm gonna do 30 hours on George Jones this year" (real example), and nobody can stop them.
IOT's format has a lot of statements, but not many questions. Bragg doesn't often say "hold on, what are the consequences of that?" (unless it's a prepared question designed to move us through the biography). Ironically, this lack of curiosity gets worse on subjects he understands well (the arts).
The unscripted chat afterwards is often the best bit. I could do with 10 minutes of on-script introduction and 50 minutes of experts discussing something they're passionate about.