The only way such change can be enforced without a war is from inside.

"Enforced" is not the word I was looking for. More like showing the ruling class that it's in their own interest to gradually apply some changes. There are many obstacles for such a strategy. But even if there isn't a clear path, there needs to be some factors in place for somebody inside to invent that path. If nothing is ever done, nothing will change.

I mean, isn’t that exactly the whole point of sanctions, to make people on the inside to feel the effects and do something about it from within?

That's the theory. The practice is the rulers will use the sanctions to prove to their people that the outside world is mean and evil and their only hope lies in their dear leaders.