Why did Allah destroy previous nations for their disbelief, but not current ones for the same reason?

It appears that the intended meaning of 'destruction' here is eradication or a general punishment. This punishment used to occur before the revelation of the Torah to Moses (peace be upon him). After that, no nation was punished with a general, eradicating torment; instead, believers were commanded to strive against their enemies.

Sheikh al-Islam Ibn Taymiyyah stated that before the Torah, Allah used to destroy disbelievers with the punishment of eradication, such as the people of Noah, 'Ad, and Thamud. After the Torah, Allah did not destroy any nation with the punishment of eradication; rather, He punished some of them or commanded the believers to wage jihad against the disbelievers.

Ibn Kathir said that the verse: {And verily, We gave Moses the Scripture after We had destroyed the generations of old} [Al-Qasas: 43] means that after the Torah, no nation was generally punished. Instead, the believers were commanded to fight the enemies of Allah. He pointed out that the punishment of eradication did not occur after Pharaoh and the revelation of the Torah, citing the hadith of Abu Sa'id al-Khudri that Allah did not destroy any people with a punishment from the heavens or the earth after the Torah, except for the people of the village who were transformed into monkeys.

Al-Sa'di mentioned that after the mission of Moses and the revelation of the Torah, Allah lifted the punishment of eradication from nations, and jihad was prescribed for the disbelievers.

As for the Ummah of Muhammad (peace and blessings be upon him), among the reasons for lifting the punishment of eradication from them is the mission of Prophet Muhammad (peace and blessings be upon him) and his mercy, as he was described in the Gospel as "a sanctuary for the unlettered."

Ibn Abbas said that the Prophet (peace and blessings be upon him) refused to respond to the people of Makkah's request for signs (miracles), fearing their destruction if they disbelieved, and preferred to spare them.

Ibn al-Qayyim mentioned that Allah punished previous nations with the punishment of eradication due to their long lifespans and strength. When lifespans became shorter and strengths weakened, the punishment of eradication was lifted, and their punishment was made to be at the hands of the believers.