Wow, It's nice to see people being passionate about the series be it for good or bad. At the end of the day everyone is entitled to their own opinion and debates are always a nice thing as long as we keep it civil.
@TrapHentai makes a really good point when bringing up how most current shonen mainly focus on a single character (the MC) , so when you have a series going against that trend is natural that some readers might find themselves confused or feeling out of place since most series go for the MC vs the world way of storytelling. I personally believe that having a story that tries to make its entire cast relevant, rather than having them just as mere plot devices for the MC to step on, has more positives than negatives, but to each its own.
I feel some people are eager to see the MC become strong so he can chase after his dad and find his sister. The thing is that it would be illogical for him to become OP just with a couple of months of training. My guess is this will be a slow paced journey and he will make steady progress during the course of his 3 years at school so I wouldn't expect him to become the top fighter of his class up until his final year, with Maria already graduated.
I think having that in mind when reading this series is a good way to just enjoy the story and characters without getting frustrated by the MC's current weakness. The harder the struggles the better will be the payoff in the end.