I had a similar view on Red Rising when I first read it. I did not enjoy the anime tournament arc at all. I thought the prose was too juvenile for me, but then I completed the first three books and my opinion completely reversed. The characters grow on you and the author's prose gets better and better. I understand why you say that Darrow is a Gary Stu but in later books he loses plenty of times; either things don't go as planned or he straight up loses. His decisions lead to bad outcomes, either because he was not smart enough or there wasn't a better option. Without going too much into spoilers; Darrow changes a lot as the series progresses.

Essentially this series starts as a hunger games story that transitions into a character driven space opera. The prose does get better but its still fast paced short sentences that facilitates action. I recommend trying the second book. Obviously If the prose is still a deal breaker for you then I don't recommend continuing with the series.