We have two semi-rational choices:
(1) Topple Assad if we have a better option, or
(2) Leave Assad in charge of a unified Syria.
I don’t see a third option that has any merit at all. A no-fly zone is too weak to topple Assad, although it is likely to extend their civil war.
Few are talking about Syria without Assad. The issue is the form of government in Syria. And the presence of Iranian forces in Syria.