The idea behind this argument was presented as the Good guys need to die because it makes it more realistic. Well philosophically realism is the belief that reality exists independently of observers. Its entirely based on common sense. In the real world and even in manga this concept has its place especially when it comes to death. In Bleach the concept of death carries weight only depending on the circumstance. Shinigami are spiritual beings their very bodies are made up of spirit particles. Shingiami means death god, they govern souls and keep the spiritual balance of the universe. According to the human definition of death they are already dead. This is a supernatural fantasy, so whats considered realistic is based on the concept of the series. Death with no purpose doesnt make a story better. You have 2 types of death: the death of a minor character that you can literally kill with no issue for the story, cannon fodder, they are a given in most stories. Then there is the death of the major character which can only take place under certain circumstance. It has to have a point, it has to effect someone profoundly. In Bleach the death of Masaki Kurosaki affected Ichigo and his family, the death of Miyako Shiba affected Kaien Shiba and his death affected Rukia Kuchiki, the death of Hisana Kuchiki affected Byakuya Kuchiki, the death of Gin Ichimaru affected Rangiku Matsumoto, the death of Kaname Tōsen affected Shuhei Hisagi and Sajin Komamura. Most recently the death of Chōjirō Sasakibe affected Yamamoto profoundly. These deaths had purpose they created a emotional response in others that very well shape them.
Actually in most stories its highly rare for a good guy to die and more often then not even if he/she did they bring them back somehow. DBZ as an example had Goku die like 2 times or so and loads of other main characters and they all get brought back by the dragonballs so how do you qualify that. Naruto while it kills people left and right, has what three main persons of any significance die for good. The greatest false concept is that killing off good guys make the story exciting cause its boring seeing bad guys get killed. By majority though in what storyline is that true. FMA: Brotherhood has many minor characters die and essentially only hughes really dying. Its an still an awesome story.
There is little death of good guys in Bleach because its simply not the kind of story that can support that. Ichigo isnt capable enough to do it all on his own, nor does the foundation of the story allow such a thing as for the Gotei 13 captains to be wiped out, considering what lays in the balance of such an action. Instead of understanding that the story is character driven (depending on how consistent Kubo feels at the time) and the characters by majority dont have that much interconnection in friendships and emotional connection to allow indiscriminately killing them off. To understand that most characters cant leave behind a legacy for those left behind to build upon. We have those who expect to see what they see elsewhere or rather what they think they are seeing elsewhere to dictate what happens on Bleach, instead of realizing the story is independent as all manga are. The idea that there should be some kind of balance of causalities on both sides is unrealistic, that would never be true in real life why would you expect that to be true in a story.