Well, part of people's issues with Unity is the fact that the company pulled some price gouging BS last year. Not going into it here, but it was all over various gaming news and forums not long ago. Also, being used by a lot of groups doesn't automatically make it good, just the best (in theory) of a limited pool of options when they chose the engine to focus on. Changing from one game engine to another is a massive pain, which Oneone1 ran into when their latest games were made with Unity instead of RPGMaker. Many more bugs than previous games on release, it took a while, and they pretty much just remade RPGMaker in Unity.