It is + adj.+that ...这种句型后面都一定要用虚拟语气是吗?

不一定。如It is true that the earth travels round the sun。地球绕太阳转,这是事实。
It's kind of you that you have helped you so much these years。这些年你帮了我这么多,你这人真好!
It was right that the temple was rescued。拯救这座寺庙是做得对的。
这种结构中的it是形式主语,真正的主语是由连词that引导的主语从句。
这种结构可以换成It is + adj。 +for+n。+不定式的复合结构。如：
It is quite likely that the meeting will be put off till tomorrow。会议很有可能推迟到明天开。
=It is quite likely for the meeting to be put off till tomorrow。