There are a few aspects that make modern day shounen manga/anime very soap opera-y in my eyes. First is much like you said filler drags things out, and ultimately means nothing to the story. The rest of what you said is exactly right, with just a bit missing. They begin to warp the story into this unbelievably convoluted thing that really loses its footing all together. Naruto as an example. In the first few arcs we had a sense of meaning to every character. We knew Naruto was special, but it wasn't overwhelming. He was a person with a story we cared about. Other characters like Sasuke, Neji, Hinata, Sakura, etc. all had important stories even if they were still a bit troupe-y. The story wasn't centered around Naruto, it was centered around children essentially being brought up in the militarized state. Then after awhile it became very mythological and the story especially in the manga began to get out of hand. The characters lost their personal touch and the entire series slipped into the pit of melodrama as all soap opera's do. Once that happened the complexity of the setting, characters, and plots melted away. A lot of the story had no emotion besides the moments that they leverage our long-time attachment to a character by threatening their deaths or giving them a challenging opponent to face and become stronger. It was like we were being told mythology of Greece without the important thematic message embedded within it.