Something I've learned as an artist is to take a critic's expertise and possible bias into consideration when receiving feedback. It sounds like a similiar approach ought to be taken when getting feedback from play testers, especially with things that are inherently subjective.
Viewing post in The benefits (and pitfalls) of playtesting
You should also distinguish between someone testing the game and someone playing the game and giving feedback. It might look the same in some cases. But there is a fundamentally different approach and different expectations.
This also overlaps, when people play games they know are still in development.