Talibans :
The problem with Talibans is that Taliban leaders don't have control on every fraction. Therefore even if some of them do sign a peace deal, they can't prevent other fractions from attacking.
And even if 50 of the leaders were in Qatar, I am pretty sure there were other leaders saying "we weren't invited into Qatar and we don't accept this deal. Just wait for the traitors to return and we shall show what useless this peace deal is." -- or something in that form.
If USA do want to get out of there, they have to sign a minimal deal of withdrawal only. And leave like the Russians.
As how I see it.