"...I recall they state that a cult has one leader, and that proves they aren't one, end of story..." - Yes, this is what my jw has consistently said. However a group of men can act as 'one' so their explanation doesn't really hold.
Walks like a duck, quacks like a duck, it probably is a duck.
If you are in a group where there is no graceful way to leave and you will be treated badly and/or shunned for leaving the group you are most likely in a cult.
To leave a mainstream church is no problem. Most people understand that people change, their spiritual needs change. You don't usually have the same teacher in school your whole life as that one teacher probably could not serve you well in all your years and all subjects. Why would your spiritual needs be any different? Most churches would be sad to see you go but members would still greet you fondly in the store or on the street. They might ask if you are enjoying your new worship service but it would be as a genuine question not a way to shame you back. If they asked such a personal question to begin with.