Why Big 3 Shonen Worked

I thought a little bit and figured out why old Big 3 era shounen were better than current stuff.

Naruto was a proper tragedy, especially pre-Shippuden

Bleach was masculinity galore.

OP, while was often silly, still had elements of proper tragedy here and there.

Naruto especially had a very well written relatable protagonists that were actually like the young people we were back then.

People would actually have user picks of Sasuke, Sakura, Hinata, Garra, Itachi and Pain because they could relate to these guys.

Show was sympathetic to young people and their struggles. They portray our Millennial generation really well, reflect our feelings and moods.

They were like us, not what out parents wanted us to be.

Naruto, Sasuke, Garra, Itachi and Nagato were all victims of circumstances as well as the system around them, that wanted to use them and then treated them poorly as things did not worked out as their elders expected them to.

Naruto complained about what their older leaders make them do as well as all the BS Konoha and the world used to have. He also wanted to become Hokage and change Konoha, change the world. Minato just left Kyuubi in him for the same reasons, 3rd Kazekage placed Ichibi in Garra (see Garra paragraph). That left Naruto to grow up as reviled by the village orphan. 

Sasuke was absorbed in his hatred and desire to take revenge on his brother for killing his parents and subjecting him to a harder life. Sasuke was also jealous of Itachi as his parents clearly paid more attention to Itachi. He is strong and talented ninja, but that often causes him trouble as it attracts to him all sort of evil people who are all after the vaunted Uchiha's Sharingan. 

Itachi himself was too overburdened by all that workload and pressure his parents and the rest of the clan make him do 'for the sake of the clan'. Eventually he snapped and just killed them all with exception of his younger brother, who he was very found of for some reason. May be because he was not like the rest of the Uchihas. Tobi later retconned it in Shippuden, but original story strongly hinted that was the actual reason. I trust it more than that lying Tobi.

Garra was made jinchuriki so that village can have more firepower compare to neighbors, that made people hate him for no real fault of his own. Eventually even his parents decided to kill him. His very caretaker wanted to take him down. 

Nagato's parents were killed in war between 3 great nations that spilled into Amegakure for no reason other that it borders all three. From there on he struggled to survive and probably would have died of starvation if not for Yahiko and Konan. Jiraiya did took some interest in three of them, but eventually left them to survive on their own. As powers of the original Akatsuki grew, Hanzo the Salamander grow worried that Akatsuki will eventually overthrow him and become new government of Amegakure. He and Danzo of the Konoha conspired and lured Yahiko and Nagato into a trap in order to eliminate them. Yahiko died in a trap but Nagato and Konan managed to escape. After a while Nagato (now Pain) indeed overthrew Hanzo and became a new power in Amegakure. Then he went on to collect tailed beasts and use them to change the world.

In contrast modern battle shounen is farce rather than tragedy.

Boruto tries to be new Naruto, it is somewhat of an official sequel. Boruto is son of Naruto, but he is more of an equivalent of Konohamaru than Naruto of the original. The only difference is that Kono was a grandson of the 3rd Hokage and Boruto is son of Naruto who is Hokage in Boruto. He has none of hardships and tragedy of the original Naruto, as privileged son of Hokage he has nothing better to do than to make stupid pranks to get attention. Naruto would never be that popular if that was all there was to Naruto himself.

Even more seriously looking Demon Slayer and AoT are rather farcical.

Eren picks fights with just everyone even when it is obvious they going to beat him. He also volunteers to join a suicide squad to fight titans on their own turf.

None of the Naruto characters would go for an obvious suicidal self-harming move. They often end up in such situation but only because their intel was wrong and enemy is much stronger than what they anticipated. Tazuna told Hokage that there are some non-ninja bandits after him, not a S-rank missing-nin. Orochmaru was clearly not of Genin rank so he should not have been among the participants of Chuunin exam.

Demon Slayer has goofy trio for a main cast. Plus Tanjiro is a kind of teacher/parent favorite pet kid. 

I did not watch MHA, but it does not look promising at all.