What have the consequences been in having the Taliban in Afghanistan?
The major consequence of having Taliban rule in Afghanistan is that it brought the country into conflict with the West. This has led to the US-led invasion of the country in 2001 and to the chaos that has continued since.
When the Taliban took power, they alienated Western countries with their (to us) fanatical ways. Their executions of people for things like adultery, their banning of music, and their blowing up of the ancient statues of Buddha in that one valley (among other things) made them unacceptable to Western governments.
Most importantly, they harbored Al Qaeda as it planned the 9/11 attacks. This led to the Taliban being overthrown by the US-led invasion. The invasion toppled the Taliban, but they still have power and are still able to resist attempts to form a new government. This has led to continued chaos in the country.
In addition to the above points, by trying to revert their society in Afghanistan to one run under Islamic Sharia law from the 8th century, women in that country, who had made some significant gains in past years in terms of their equality, access to education, etc. were thrown back in time to where they were required to wear a burqa, be completely subservient to their husbands, and could suffer the death penalty if they were victims of rape. It was as if the entire society was forced to go back in time.
Even today, when they are not in power in Afghanistan, the Taliban release poison gas into girls schools, or just outright blow them up, regardless of whether the innocents inside are hurt or killed. They practice the most intolerant and strict brand of Islam there is.