First of all I would like to tell you the order of Allah Subhanawata'la in Quran Surah An'am 6, Verse No.159
Verily, those who divide their religion and break up into sects (all kinds of religious sects), you (O Muhammad SAW) have no concern in them in the least. Their affair is only with Allah, Who then will tell them what they used to do.
Means those who are divided into subdivisions of Islam Or into sects of Islam he has nothing to do with Prophet PBUH. And a person who is nothing to do with Prophet PBUH where he will go you better know. But mostly sects of Islam says if you are Kalma-go Muslim means if you have already given shahada (witness) "There is no God but Allah and Prophet Muhammad SAWW is his messenger" will definitely go to Jannah. On the contrary Allah says in Quran surah Yusuf ch. 10 verse no. 116.
And most of them believe in Allah except (as) they are associators (of other gods with Him)
We will say them a Kalma-go mushrik because they have other associator of Allah too.
Usually, people blindly follow sects in our society because they see their elders and forefather doing the same. The majority of people in our society simply follow the Deen of their forefathers just like the people of Makkah did 1449+ year ago. Different group of Muslims kept different names and titles other than Muslim because that is what they are taught to do.