I've learned a few things in my life. Many people have different taste and preferences and you can't satisfy everyone. Maybe the idea you had, was just only for a selective of people and not the majority. Is this a bad thing? Well, it depends. Does it affect you? Brings it down the moral to continue? Like
Synx said, if money is the biggest drive, then you can lose very fast your motivation.
Money should also be a secondary thing. First you need to build up a fanbase, something that people want to play and want to have. If people doesn't like your game, ask them why with arguments. Only this way you can learn from it.
As for the renders, they look fine in my opinion. They aren't great but also not ugly to look at. Many games use the same quality renders as you did, which is fine. We are all hobbyist and not some triple AAA developers with a big budget. But to be honest, when I create renders, I also think it's not good enough.
I also want to start with a novel, for almost a year now. I haven't started yet, because i'm still learning and I also think that my renders aren't good enough. I also have the feeling that people might not like what I want to make. So, I also invested a lot of time in improving my renders. It's always easy to give some good advice and say "Oh, your renders looks fine" and meanwhile i'm not proud of what I made myself.
Everyone has this kind of unsecured feeling in their life and we can't do anything about it, so it shouldn't demotivate us. If I was in your shoes right now, I would ask the opinions from people who played your game, put all the feedback together and then decide if you wanna start all over or continue your work. You can also give your whole work a overhaul, that could also work. So you don't have to start from scratch.
Here is one of my most recent render. It cost me months to get to this point and I still think it isn't good enough. But it shouldn't demotivate me. Two of my characters i've created.
Here are more, i'm going to post some more renders soon. Give it a look, and see how even I can improve with renders without any expierence in gaming development.
https://f95zone.to/threads/what-do-you-guys-think-about-my-renders.110866/#post-8124357