I agree with this sentiment. The band used by AM has limited bandwidth, but I think it has enough bandwidth in a normal broadcast channel for useful programming. AM band capable HD radios seem widely available on the auto market now. The choices of portable and tabletop radios is very limited, but I think that is a niche market anyway. The Golden Age of Radio is far away in the rear view mirror now. The AM band is just another medium for audio programming that has to compete with the FM band, Satellite radio, Smart Phones and Smart Speakers.
I think WWFD is taking the right approach. Broadcast digital-only. Using hybrid mode just uses too much bandwidth. I might be wrong but it seems like a lot of "AM" listeners are listening through FM translators these days. The AM broadcast is being used as a placeholder for the license. Given that, it seems like going digital in the AM band isn't necessarily that risky from the standpoint of listenership. It's more that the capitol investment for the digital broadcast facilities is the risk.
On the other hand, not investing in HD AM radio will just steepen the decline of the AM radio band. Audio programming listeners will just switch to other media for their audio programming. I don't think listeners will stay on the band if stations stick to analog broadcasts. That's my two cents.