B29s were designed to fly at altitudes too high for Japanese fighters and flack to reach. The development of the B29 required a bigger investment than that of the Manhattan Project. Each bomber cost the equivalent of some hundreds of million dollars. It was thought that they could then bomb targets accurately with impunity.
Unfortunately, their bombing was wildly inaccurate and analysts and commanders thought that the crews were dropping their bombs well away from targets to reduce risk to themselves. It was finally discovered that there are air currents running at hundreds of miles an hour at those altitudes that made the bomb sight calculations wildly inaccurate. Those currents were named the jet stream. Because of the jet stream those B29s were forced to fly at much lower altitudes in order to deliver their bombs accurately bringing them into range of fighters and flack.
My Dad piloted a B29 in that campaign called Honorable TNT Wagon. I have pictures a flight engineer on his crew took from the cockpit and you can see flack all around. Dad made it back or I wouldnt be writing this.
My Dad flew in WWII, Korea and Vietnam, ANTIFA all the way.