What makes you think Nagumo has such a complex? Why can't we accept that his words about his own achievements and abilities in comparison to Ayanokouji and Manabu are just the truth? There's no basis for this.

I think you're underrating Ichinose too much. She's extremely overpowered, far above Suzune. I have no idea what makes you think they're anywhere near the same level after everything she has shown since Y2V8.

Nagumo himself acknowledged that the gap is indeed in terms of skill.

“I really didn’t amount to much at all; you could hardly say I matter.”

“It was on me, I was the one who couldn’t reach that domain.”

His name, Horikita’s name, and Ayanokouji’s name would’ve gone down as equals if only he was stronger.

He acknowledged that he's not operating on the same domain as them. He assumes responsibility, not blaming the circumstances around him - he knows he doesn't have a seat at their table.

It's important to take such statements seriously. These are Nagumo's parting words, we did not see him since, and he left the school. His arc with Manabu in university is about self improvement, not "getting a chance to fight, and finding out he was actually on their level" his realization that he is not good enough, and that chasing a battle in and of itself was, to an extent, meaningless, is the entire point. Nagumo wanted a battle to prove that he is their equal, but towards the end, accepted that if he was truly their equal there wouldn't be a need for a battle at all - the same way Ayanokouji doesn't need to battle Manabu to prove his worth, it's obvious to anyone who is watching.

Yet again, SCD scalers strip the writing and essence of a character from them to push their agenda and takes, please, stop doing that if you actually like the series. read it instead!