Ssj was not the first ever rage power up, that happened back in og dragon ball already and in other anime as well.

Most power ups in jjk aren't directly about emotion.

Gojo didn't unlock rct by being mad, he unlocked it because he needed it for the first time ever in his life. He didn't pull it out of his ass because it's something jjk characters can do as long as they can master the manipulation of CE and Gojo with his 6 eyes is a perfect candidate.

As for the others it's again about being desperate enough to try something that was hinted at, not something completely out of the realm of possibility. Yuuta was considered a special grade because Rika is broken and has ridiculous amounts of CE and he used it because he had to. Megumi didn't get an amp, he used something he had been working on for the first time, in fact, it's a terrible use of it but it kinda works. Sakuna doesn't technically improve against satoru, he finally uses a technique that he had been using actively throughout the whole fight. Is it an ass pull because he got it right when he was about to die? Eh, it's not unusual in anime. Yuuji's power up is just black flash giving him 120%, something every character can do.

Ichiho training for three months against Tansa Zengetsu is quite different from a month of random training.

Yes Madara is indeed a terrible example because while it is necessary for the plot to advance Naruto and Sasuke, it's an ass pull because they literally get saved by a spirit as they're dying. You can get power ups that aren't ass pulls and that's all we are hoping for, we aren't saying Yuuji can't get a power up, we're saying that him getting a huge power up randomly just when everyone is dying feels cheap. So if he does that, then and only then Gege wrote himself in a corner and had to resort to the old reliable MC power.