You're a silly billy of course. Mitsuru is not supposed to be a guy you WANT to self-insert, he is the guy that you know is your self-insert. The whiny little shit who is all talk but no bite. The not so competent one. The one who does try, probably even trains hard, but isn't miraculously better and more capable. He was the guy with clear limits. Still, he is the guy who does want to be better, and did have a role model. Hiro is the guy Mitsuru wish he could be, as in, Hiro is the guy the normal enthusiasts represented by Mitsuru wishes could be.
He was the biggest Hirofag ever, after all, turned whiny edgy bitch who hated Hiro for childishly stupid reasons afterwards.
That's what makes Mitsuru such a good character overall. He isn't the unrealistic supercompetent otaku insert. He is the realistic rather pathetic otaku representative. He is not smarter. He isn't stronger. He isn't better. He's not even the most handsomest (I would argue that Hiro and Goro are more handsome overall).
Mitsuru was the one who tried to understand the hobby, but simply failed, and actually never really got into it for the sake of the hobby itself, but because of that one good friend. The one who drops out of it after he's grown up, and chooses to stop doing something that he's not good at. So he goes his own path.
You don't need a boisterous personality to be interesting. One shouldn't misunderstand being a petty arsehole and false bravado as positive traits. It is not words that ultimately mean something, but actions. And sometimes, deciding to stop really does mean knowing when to go forward.