Welcome to the world of professional character design.
That goes with the territory. Neutralizing your characters and finding that 'safe' area that clients sometimes look for. This is part of what you do and it does take skill. It may not be fun, but it is still a challenge.
I can't tell you how many times I've presented really unique and appealing designs only to have them watered down by the opinion of a single individual or a committee of people who were marginally qualified at best.
Back in the day when I presented my portfolio for work, the images consisted mostly of designs I had done on my own. Much of what I did professionally was unusable. It's ironic, as the art that got me the job was work from personal projects along with the choicest stuff that came from studio gigs, and a lot of that consisted of development art and rejected designs. Then once I got the gig, it became a process of neutralizing characters. Not always but more than I care to remember.
The key to succeeding in these situations...
1. Emotionally detach yourself from the project.
2. If you really need to do the project, then do your best to give the client what they're looking for. Even if it means compromising on principles that you know will make the character/s more appealing.
3. Try as best as you can to educate the client as what makes a good design, and why giving a character an edge, even if it is a subtle one, will enhance and strengthen the character and create more appeal.
4. If this doesn't work, keep your mind on the financial compensation you're getting.
5. If that doesn't work, be sincere and excuse yourself from the project. Tell the client this isn't the kind of project you're suitable for, and vice versa. I don't recommend taking this approach, but sometimes it's the only alternative if you can't get your heart and mind into it. Unless you need the cash and the work experience, you may be better off walking away from projects that you're not able to get into with enthusiasm. You want to give the client everything you've got to offer. If you're not able to do that, maybe the client can find an artist better suited for the job and you can find a project that will bring the best out of your art and encourage your creative and artistic growth.
I suggest sticking with it and doing the best you can with what you've got to work with.
It's not as bad as you may think it is. Be sure to draw plenty of your own designs on the side. It'll help to keep you sharp.
Good luck!