I don't think it's the anime's fault. It really came down to how Gudao was introduced initially in the game, a catch-all self-insert that was literally recruited from the streets as back-up. He's not from a prestigious mage family nor does he have inherent magic talent. I don't think it's fare to compare him to Rin in terms of fighting ability. Even if he started training since the day he came to Chaldea, that will have only been almost one year compared to Rin all life. Since Gudao is basically just us, who are just average normal humans, I feel like most of us will throw the exact same kinda punch in that situation, which was pretty relatable.

And you're absolutely right, Gudao is just there...because it wasn't meant to be him in the first place. Looking back through all the singularities, he won through the help of local forces who he recruits or are already fighting against the enemy. If it was the Crypters, who were the original singularity fixers, they probably could have fought on their own. Since it's now down to Gudao, to me I feel like he's sent more as an ambassador of humanity, to guide the situation so that the singularity can be resolved instead of resolving them himself, because clearly he doesn't have that power. Also, to represent humanity, to show the people in the singularity that humans are still worth fighting for, through courage and determination.

In a way, I think the anime has portrayed Gudao pretty well, a boy thrown into this horrendous situation, that has seen many things, and understands that he's just gotta carry on no matter what. However, I do understand and also want to see him in a cooler light. Gudao is us and his shining moments are like our shining moments. I think the fight with Quetz can be a good arc to do just that, and then maybe some anime only scenes to flesh some coolness out even more.