This may be the only place I've ever seen people claim that voice acting doesn't matter. If it didn't, we would still be making silent movies. Companies would not spend millions to voice their games/movies/series if no one cared. And it IS a skill. Japan literally has voice acting schools. A good voice actor can add so much emotion to a scene, or use different tones to change the meaning of a phrase, give insight on what the character is feeling or thinking or portrait sarcasm for example, without the need to pause a scene with narration. Bad ones will sound like your GPS, monotone and emotionless at all times. So you can't just pick randos off the street, much less use AI. This does not mean a VN can't be good without VO, but like... books can be entertaining even though they have no music, no images, no gameplay elements or choices. Does that mean every game on this site would be better as a book? I doubt it.
As for the problem with the game, the issue is lack of experience (at making games), poor direction, and overambitious marketing. Taken individually, the different parts of the game can be fine, but put together it's a mess.
Take the story for example. Rebels trying to bring down an oppressive government isn't very innovative, but it's fine and you can take it many different ways, there's some ok worldbuilding, the main characters are somewhat interesting... but then they ruin everything with the tone they adopt. How are you supposed to take the story seriously when the characters themselves don't seem to? Everything has to be or end in a sex joke. Like you'll have a serious scene about the political machinations required for the empress to keep the empire in line, then go right back to dildo superweapons and swearing every other line. And even if the humour was exceptional (it's not) when there is only one kind over dozens of hours non-stop, it gets old fast.
Similar thing with the land and space battles. On their own, it's not particularly exciting gameplay, but it's passable. Certainly better than most minigames H-game devs put in their VNs, and if it was just a minigame during main quests you only do a handful of times, no one would complain. But it's not. They are everywhere; main quests, side quests, exploration. And you need to do them hundreds of times to fully level-up your crew members, but there's basically no progression, no variety, little challenge or reward, so again, it gets old fast.
And the issue with the sex scenes being completely disassociated from the story and gameplay has been stated enough times.