Only Those Who A Messenger Came To Go To Hell?
If you see it in continuation of verse 6, where it specifically mentions about people who did kufar and next verses ( 7 to 11 ) further elaborate their condition. As far as technicality that you mentioned, the message of religion has been preserved in its pure form and so is establishment of last Adalat, the rest will be judged by God on the day of judgement whether itmam-e-hujjah happened on later people or not and if yes, then to what extent and we all will be dealt accordingly with justice. Following related videos might of some interest to you or other readers Please refer to the video below from 1:00:08 to 1:03:09 https://youtu.be/u9S64cSYaUg?t=3608