I've read the translated light novels. The story only picked up and showed the depth of the characters after the revelations in volume 5. This is common in the fantasy genre that needs time for world building and time to slowly build backstory. Seriously, I think the anime was only the beginning arc of the story (LN volumes 1-3). Its no surprise that the manga that barely covers volume 1 cannot show enough depth.
I estimate that around a hundred chapters from now, will we see that there are several enemies, much more powerful than the MC. Call them level 100. However, in the genre of battle mangas, the author needs to show enemies one level at a time. If the MC immediately triumphs over the strongest person in the world, that wouldn't be fun. The story will end quickly! We wouldn't be able to savor the battles with mid-level characters, at level 30 or 50.
I think the fanservice is standard in the genre, but the author uses it well. Usually, virgin MCs stumble into the scene then get punched to the stars. Hentai MCs would escalate things quickly. The MC of this story uses it to loosen up the stress in the girls. In self defense, he also strips girls instead of physically hurting them. The author strategically places them in points where the story is very tense in order to diffuse the heavy mood.
If you're sick of useless male MCs (common in harem and shounen romance), Akatsuki is a refreshing male lead. Like Keima of World God Only Knows, he truly cares for the girls and knows how to handle a harem. Like Issei of Highschool DxD, he is perverted, but can always be relied upon to save the world and the girls he loves.
I repeat, this is NOT a Gary Stu or pointlessly overpowered MC. The story simply starts at the midpoint, after he has already overcome powerlessness. I think the story's true theme is exploring what it means to be a true hero. In Akitsuki's actions, attitude, and principles (aesthetics), he'll demonstrate that.