Do you think the X-Men are effective in executing their goals and / or which goals do you think they execute best?

The X-men are a very gray area team. It's not that black and white imho. There's several situations where everyone was executing their goals properly and they made the situation better and there's times the very same goals burned in flames. Not to mention since this is a fictional or more specifically comic book universe, you have people from all across the multiverse interfering with their plans. Like Bishop came back to prevent Age of Apocalypse from happening. Rachel came back to prevent Days of Future Past. And the list goes on. They are both a strike force and vigilante group. More a vigilante group because none of them (as far as I am aware of has had practical military training apart from Wolverine.) And Wolverine and a few others iirc were involved in mercenary work among other things. They all have a long list of expertise and weaknesses and but they don't always use them as a well oiled unit let along strike force. They try to be a strike force alot of times succeeding but there's alot of times they do not. It's very situational based for them. So basically my point is they are all of those things and more. The xmen at their core are a bunch of misfits trying to belong and feel wanted by proving to humanity mutants aren't all bad but they all have different visions on how to do it.