They believe that the message is to be followed directly which to them is following the Messenger. Meaning they don’t need the Messenger to show us how a command is to be implemented. Every layman can interpret the message on his own personal interpretation and derive conclusions. See below Q&A:
How does Kitabtullah portray the relationship between the message and the messengers?
A: One message and many messengers. Following the message is in reality following the messengers. Please see Ayah: 14:44 (Source website Q&A June 2021).
True Belief
AllahSWT has sent about 1 lakh 24 thousand ProphetsAS in this world. Not all of them were given a Book or Message, yet faith depended on accepting the Prophet / Messenger and the majority of people who denied the Messenger were severely punished in this world. As AllahSWT has said –
And, of course, a messenger from among themselves had come to them, but they rejected him; so the punishment seized them when they were wrongdoers. (S16: 113)
Belief in the Seal of the ProphetsAS is not optional. Anyone who denies the ProphetSAS but still follows/ed one of the previous “Message” is a Disbeliever without doubt after his appearence. All previous laws were abrogated after the appearence of our ProphetSAS this is clear as daylight. There is only one Messenger to be followed who brought the last book of Allah and showed the believers how to put the message in practice. We accept and believe in all Messengers of AllahSWT as truthful but none can achieve faith without obeying the ProphetSAS as AllahSWT commands the believers –
Say: “Obey Allah and His Messenger”; but if they turn back, Allah loveth not those who reject Faith. (S3:32)