WWII bomber engines were some of the most complex engines ever manufactured including jet engines in the list. The part counts as well as tolerances were very high while reliability was a bit troublesome. The old saying goes if it's a radial and not leaking oil, something is wrong. This and the weight accounts for the reason they are no longer preferred over small turbines in large-prop installations. If you have the tooling required to produce the part tolerances large radials require you might as well make turbines, which is what the Germans started doing about this time. The reason large radials persisted to the end of the War is that turbines were not quite ready for battle and the War was too intense to allow their discontinuation.
My favorite is the Pratt Wasp Major with 28 cylinders as a working cutaway display at Southern Museum of Flight in Birmingham, Al but there are quite a few displays around. They were wonders of engineering at the time, and even now attract attention. There is a link lost between the piston and the jet in terms of appeal and advanced pistons were more approachable because they share technology with the earliest internal combustion engines.
Here is a great pdf article explaining
how Wasp radials were balanced.