I know you guys are focusing on 6s here, but just wanted to throw my hat in as the creator of Glassworks.
I did everything I could to have it tested as thoroughly as possible. I did high level, extensive testing for about a year before it's debut in UGC this past season. I poked and prodded as much as I could just before the season started to get as many eyes on the map as I could.
Then as soon as it's week came up, suddenly all the people who hadn't cared to look at the map yet started paying attention and taking issues with it. It was dead silence until just before their matches, and suddenly the map was to blame for their losses and half the league seemed to have problems with it. The commonly thrown around notion was to scrap the map because it would always be "terrible."
I'm not saying it's perfect, it has room for improvement, I got some valid feedback that I plan to implement, but after two years of development on the map, getting it dismissed on a passing glance is frustrating. The actual legit issues could've been found had more players bothered to look at new and upcoming maps and taken time to provide feedback to them. It's hard for mappers to see their map the way the players do because they have been so close to it for so long. If you want solid maps, the feedback loop has to happen.