I think the people here in the comments are comparing this series too much to Claymore and are quick to pass it off as it were some generic shounen that you read up in anything published by Shueisha's Shounen Jump Magazine. Guys, it's anything but generic and deserves a little bit more praise than you think. If we place the Shounen genre or a manga targeted to the teenager demographic nowadays, you'd be placing the generic titles under Shounen Jump series or those god awfully redundant Isekai trash that gets so overrated in this site too much.
This series stands out from the rest, departing from the classical Tolkien-inspired Medieval Fantasy that has been so overused to the point that authors have begun pulling ideas from their asses without much thought. Ariadne in the Blue Sky is much different and although there are swords and "magic" the series is clearly one in Science Fantasy, which I haven't seen too often in Shounen manga. It's why you have guns, robots, bazookas, and modern cities in the series. Having read mangas since 2013, I can say for sure that this series does a lot of things well and each arc has a lot of fresh ideas and new scenery to enjoy. If things feel too childish and has lotta videogame elements present, well it's mean for teenage kids, what did ya expect? One thing's for sure, its not mediocre in anyway.
You can expect an author to write a story targeted for teens to be filled with deep life lessons and philosophical themes and gore like Claymore, Berserk or Attack on Titan (which is an exception).