This thread is starting to take sides and I don't think it has to be that way.
Are there parents who wear rose colored glasses and are the biggest complainers? Yes - we have all run across them.
Should some coaches be doing something else? You bet.
Those are the extreme cases. We don't need to argue those points because we all know they exist.
One thing parents try and do sometimes is project their kids into the hs starting lineup based off of summer/travel team experiences. Our high school had several summer teams funnel into it thus the freshman team was a composite of those teams. Should one of the summer team coaches be the final arbiter of who should play and who should sit? How do the parents know exactly who should be playing and who should be sitting?