The scholars have clarified this issue. And the hadeeth is not weak.
From Anas that the Messenger of Allaah (sallallaahu ‘alayhi wa sallam) said:
"The Children of Israa’eel divided into seventy-one sects and the Christians divided into seventy-two sects. And my Ummah shall divide into seventy-three sects, all of them being in the Fire except one sect."
[Related by al-Haakim in al-Mustadrak with the Talkhees of adh-Dhahabee (1/128), it is related in Majmoo‘ul Fataawaa (3/340) and (16/491) of Ibn Taymiyyah and ash-Shaatibee in al-I‘tisaam (2/189-191) and by al-‘Iraaqee in Takhreejul Ihyaa (3/230) and Ibn Hajar in Takhreej Ahaadeethul Kashaaf (p. 63). It was authenticated by Shaykh al-Albaanee in as-Saheehah (no. 203-204, 1492) and in Saheeh Sunan Ibn Maajah (no. 3225-3227) and in Dhilaalul Jannah (no. 63-67).]
The Prophet (peace and blessings of Allaah be upon him) also described them in the following terms: “My ummah will split into seventy-three sects, all of whom will be in Hell except one group.” They said: Who are they, O Messenger of Allaah? He said: “(Those who follow) that which I and my companions follow.” This is mentioned in the hadeeth of ‘Abd-Allaah ibn ‘Amr which was recorded and classed as hasan by al-Tirmidhi (2641). It was also classed as hasan by al-‘Iraaqi in Ahkaam al-Qur’aan (3/432), al-‘Iraaqi inTakhreej al-Ihya’ (3/284) and al-Albaani in Saheeh al-Tirmidhi.
Authentic hadiths, tirmidhi and so-forth. I could go on but I won't.
I'm studying an alim course so I don't take my sources from internet especially when these sources are authentic from several scholars.
You think those that create their own sects will taste jannah? What a joke. No laymen, me and you can refute that from scholars who have worked their entire lives for the basis of deen.