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Uchiha fan mad about 1 of Minato's abilities and trying to downplay him more than the manga did via exaggeration: double check.
All right, first off, it's not wanking unless it's contradicting what the manga said. Here's what the viz translation said according to BlinkST, who runs the viz scan sticky. Kakashi: If I recall sensei, senjutsu is not your specialty. Minato: That's an understatement, It takes too long to knead that chakra, and I can't maintain it for very long. Truth be told, I haven't used it much in real battles.
manga facts.
1. Minato is not good at senjutsu.
2. He is a true sage as seen with his eye pigments.
3. It takes longer than he likes to enter SM.
4. He stated that he can't maintain it for long
5. He said that he hasn't used it in real combat much, meaning that he has used it in real combat.
Conclusion: Minato is bad at sage mode because he takes up time entering it and it doesn't last long. However, he has used it before in real combat, meaning that any argument a hater or Uchiha trad makes about him not being able to use it is null and void because it's clear that he can in combat conditions from the statement he's made about his past. Unless the fan says Minato can last a long time in it, he's not wanking him, but utilizing a toll of Minato's limited as it may be. In that situation, it's you, the naysayers that breach manga facts to support your dislike.
I'd like to also add that "Minato can only maintain it for 5 seconds" is pure speculation invented by haters. We have not seen Minato in the process of lossing SM after being kicked by Madara, therefore, saying he lost it then and there is pure speculation. It's not more founded than saying his SM lasted for the entire conversation between Madara and Obito until he was shown without it. Haters just want to go with the minimum because they feel threatened.
2nd, Minato's better than Jiraya. Jiraya was an imperfect sage while Minato was a true one. Jiraya couldn't enter SM on his own, Minato has demonstrated that he can.
Pure, unadulterated, unbiased assessment of the manga facts.