I have run the 1340, and 2800. Plus several of the Wright engines.
I believe technology just surpassed them. With the advent of the turbine, we have just bypassed the radial engine technology. The turbines on turboprops can simply fly for longer TBO, get better fuel economy (longer range), weigh a lot less, ease of maintenance, and in some cases produce more HP than the radial.
As for TBO's, the 2800's we use today get around 200 hours, then we rebuild them to prevent items from wearing out and needing replacement. Parts are just getting very hard to find.
FYI, on the 2800, the magnetos are mounted on the forward reduction gear cases. Same for the 1340. As for changing them being a pain, naw, you just need practice doing it, thats all. Once you have done several you learn the tricks of installation.