Ugh, seen that happen way too many times.

Feel your pain on this one. Pushed hard into flat design for a client project last year and got the same "it's sterile" feedback. Started playing with adding just one textured element or a warmer color spot to break it up. It kept the clean look but gave it a bit of soul, you know? Maybe the trick is using it as a solid base but not the whole meal.

Actually, this reminds me of when I tried to put together a bookshelf without looking at the manual. Had all the pieces laid out, thought I could wing it, and ended up with extra bolts and a wobbly mess. Spent an hour fixing it, but if I'd just spent five minutes reading the steps, it would've been done right the first time. Now I always check the instructions, even for stuff that seems obvious.