When you leave a villagers house and they ask you what you think, does your answer do anything? I always say it's great to be polite but was thinking maybe if I tell them it's ugly they'll change it up?
Someone correct me if I'm wrong, but telling them it's ugly won't make them more likely to change things up. The villagers changing their houses is sort of random and doesn't change based on that. When you tell them you like their house, they'll also sometimes say stuff about wanting to keep improving their houses.
The only thing it does is affect your friendship level with that villager.
I'd recommend always saying their home is great, especially considering the fact that you can get some pretty cool stuff if you do. I got a throne from Mira before for complimenting her house. So even if it sucks, go for it friend.