Most people have an unfortunate tendency to project their own values and preferences onto the world at large, and fail to recognize when they cross the boundary out of their own spaces and into other people's.
Recognizing this means advancing solutions that primarily aim to minimize conflict among many parties, each pursuing their own particular concept of the good within their own boundaries, and avoiding trying to universalize any singular set of terminal values.
Attempting to pursue solutions that depend on everyone agreeing on the same set of terminal values will always fail, and will often generate intense conflict that escalates well beyond the bounds of the original question and causes a great deal of collateral damage.
Yes, that's called compromise. It's basically one of the foundations of society and civilization. It's not a blocker for public-interest projects.
Far from being the opposite of idealism, this approach is in fact the only one by which high ideals can be approximated in reality.
> You seem to be complaining that something is impossible because it can't be implemented in a perfect utopian way.
Quite to the contrary, the complaint is not merely that the pursuit of these goals would fall short of perfection, but rather that the consequences would largely be the inverse of the intentions.
In essence, idealism is its own opposite -- if you're looking for a single word to describe this critique, some good options might be "correctness", "efficacy", and "reasonableness".