I'd say a good majority of players have never played prop yet voted against it. most people haven't played gran since voting in esea either, yet they vote against it too. I don't understand how you can have an opinion on a map if you haven't played at least (note I said at least) a couple of times to truly get a grasp on it.
I'm not saying that those who have played it and have the opinion of it being bad are wrong, but I am saying that many people haven't and voted against it since they don't want to learn a new map.
People will play worse on new maps because they haven't become accustomed to it. Many people blame their bad play on the map on the first playtest then never play it even though they didn't even have a chance to fully grasp the map. People tend to think maps are too big or have too many doors on first playtests because they aren't used to covering everything or know the good pathways or jumps to cover ground the best. Most of the maps tend to be as big or smaller than process. Koth maps tend to be as big or smaller than viaduct. Maps seem to have too many props because they haven't learned how to traverse the map backwards as they have with every other map.
I remember there was another thread regarding how to fix granary, and dagger released a new test version that literally fixed most of the issues that people agreed upon in the thread, and then most of those people complained about those changes that were made and how dagger should revert it back even though his changes were good changes based on feedback.
edit1: another good example of this is koth_bagel. Many people tried to play bagel like viaduct and called it a shit map. But that map isn't good for scouts like viaduct is. Every strong scout position is easily spammed by demo or easily contested by a soldier. flanks are indoors with more splash options and high ground awnings are smaller so its harder to maintain the high ground as a scout. As such you need to be much more soldier-centric, but when it was on pugchamp and picked, everyone thought it was so awful because they'd tank their scouts like viaduct and run them through the chokes of bagel and get annihilated.
TLDR: people don't want to learn how to play maps, yet vote against them. granary is fine just learn how to play it.