Is the world harsh, or have people's hearts hardened? And what is the evidence for that from the Quran and Sunnah?

The verses and Hadiths condemn this worldly life, such as the Almighty's saying: {Know that the life of this world is only play and amusement, pomp and mutual boasting among you, and rivalry in respect of wealth and children. It is as the likeness of vegetation after rain, thereof the growth is pleasing to the tillers; soon it withers and you see it become yellow; then it becomes dry and crumbles away. And in the Hereafter there is a severe torment (for the disbelievers) and (for the believers) forgiveness from Allah and (His) good pleasure. And the life of this world is only a deceiving enjoyment} [Al-Hadid: 20], and the Hadith (definition): "Indeed, the world is cursed, and cursed is what is in it, except for the remembrance of Allah and what follows it, and a scholar or a student."

However, several points should be noted: 1. The world is part of Allah's creation, and it is a manifestation of His attributes, power, and wisdom. 2. The world is a cultivation ground for the Hereafter. It is not condemned absolutely; rather, it is a dwelling where the believer earns mercy and Paradise. The best of people are those whose worldly life does not distract them from their Hereafter, nor their Hereafter from their worldly life. 3. Love of the world causes hardness of hearts, because preoccupation with it distracts from the remembrance of Allah and obedience. Allah has differentiated between people of knowledge and people of worldly professions in terms of purity of hearts. 4. One must be careful not to curse the world or time, because Allah is the doer of adversities, and cursing time is cursing Allah the Almighty.

A Muslim is advised to busy himself only with what benefits him through obedience to Allah, not to complain much about people, and to make the world his mount to the Hereafter. He should be grateful in prosperity and patient in adversity, and enjoin what is right and forbid what is wrong. Allah has made the world for the believer to provision himself, for the hypocrite to adorn himself, and for the disbeliever to enjoy.