The ones who are speaking here is the human beings who did not believe in the Day of Judgement. As Allah (swt) says:
﴾وَيَقُولُونَ مَتَىٰ هَٰذَا الْوَعْدُ إِن كُنتُمْ صَادِقِينَ ﴿
(And they say: “When will this promise (i.e. Resurrection) be fulfilled, if you are truthful?”) (Yaseen : 48)
The ones who disbelieve and deny the Day of Resurrection have always had these arguments, and still having them up to this instance and will continue having them. As we know, one of the most important elements of faith is the belief in the Day of Judgement. Because of this, the last Juz (part 30) of the Book of Allah (swt) focuses on the topic of the Hereafter. In this last part of the Holy Qur’an, the Surahs are arranged according to Allah’s (swt) will (tawqefi) as they will be the last to come to a person’s ears. Furthermore, these last verses will also be the ones which are the most recited and memorized by humankind. Thus, Allah (swt) has willed that they remain in remembrance of the Day of Accounting.
It is not enough for you to just say that you believe in Allah (swt), in the Angels, Divine Books and Prophets, this is because, the more important thing after saying this is to know that you will be accountable and that you will return after death to a day where you will stand in front of Allah (swt) .