The advantage of this game is there are no mingames, you don't have to check every room and every corner like in many sandbox games
Playing a game with so many girls, paths and events in a visual novel style would be more difficult in my opinion.
The player can decide which LIs to seduce first and the events of which girls player wants to see first, which would be limited by the plot in a visual novel. Getting to the lewd two girls events (an example is Lina+Rachel) would also be limited by the VN, as player would have to get to a similar place in both girls' paths, which would take a long time due to intertwining events of other girls. Events of LIs and side girls would have to be intertwined, watching several different events to see the girl player want at this moment would be annoying
In addition, each path contains separate events and separate plot threads related to the paths we choose for other characters, also by choosing different paths we learn different things. In example, by sending a girl to RM Sakura becomes more open and says new information, which is useful in the investigation. This would make VN even worse thing to create and connect threads to, i won't even mention the timeline.
I dare say that it is a sandbox and a simulator at the same time.
Thanks to the sandbox, MC can work out at the gym and shower with Lina every day, sleep with Evelyn every Friday night, visit Monica in her office, ect