The idea to rope Afghanistan in to the B&R sounds good on paper. But Afghanistan is probably one of those places that is almost ungovernable.
There was a plan by to develop the Afghan cashmere industry which failed. There was a plan to provide cargo planes to Afghan government, again failed due to corruption. The entire US plan to rebuild Afghan infrastructure basically failed due to rampant corruption and incompetence.
At one point the US military was trying to turn farmers that didn't even have grade 1 level reading skills into disciplined soldiers. There were regular reports of Afghan police or military high on heroin, nodding off at checkpoints. Or how Afghan government employed young boys as sex slaves. They were called Chai boys.
The nickname for Afghan government was VICE - Vertically Integrated Criminal Enterprise. The Taliban and these local warlords are no better. 穷山恶水出刁民. The entire country is a bottomless money pit.
Well the same can be said for many of China's other BRI activities in various other 3rd world countries.
Take Malaysia as an example. China signed a number of BRI deals with their ex-PM, Najib Razak, perhaps the most corrupted PM in Malaysian history. The deals are negotiated by that man to enrich him and his family. Then when Najib is voted out of office, another corrupt PM, Mahathir returned to power, and who is anti-China. He decided to cancel a number of major projects signed with China after years of negotiations with the previous PM, citing corruption. Sounds correct, but he also neglects to mention that China is more than willing to renegotiate those deals. Now, Malaysia remains the only ASEAN country which had so publically rejected BRI projects. Its the only remaining stumbling block to connect HSR lines from Kunming to Singapore. Its economy is going backwards relative to the other ASEAN countries. Where was America, the West, and Japan to step in when China is pushed away? Nothing! Its pure Malaysian arrogance and stupidity. Meanwhile China and the rest of ASEAN just moves on. There is no need to teach Malaysia a lesson, they are in trouble and have still not woken up. Let reality do it's work.
Point is, not every country is deserving of BRI. Afghanistan might probably the latest example of a bad BRI investment. China's may be too optimistic. But its technically not a bad idea to propose BRI to Afghanistan. Both for soft power, and to stabilise the country in the long term.
Only time will tell. But I think China has taken lessons from its other BRI mistakes. There isn't a rush from China commit too much into Afghanistan yet. There is also some military coordination between China and other SCO members, bar India to prepare for an eventuality that Afghanistan might return to being a failed terrorist state.
China doesn't need Afghanistan to continue growing the BRI. But its still nice to have that country join up because of its history with the old Silk Road. Its up to Afghanistan to make its own BRI happen. If it can't, then too bad. China will have to move on. Just resume the current BRI program that is not passing through Afghanistan.