That's a great question. So if you look at all the good the church does and say "I like the idea of this" and but your pro LGBT so you don't like that aspect of the church.

I think that's a personal choice at that point. You have to weigh the good vs the bad. For me it's a clear choice. Mormons mostly only help other Mormons and you lose that help if you stop paying your tithing. So to me it seems like a membership you pay to be part of a community that can help you. But that same community hurts people. So with the idea that it's a paid club that helps each other, it doesn't justify the harm it does. Especially when that harm is done by forcing their views on others.

As for changing it from the inside, I don't see a lot of room for that. They have a living prophet selected by God. What they say goes, and the church is very big on rules. Historically the best way to force change for them has been external, social driven pressure around things like black priests and such.