Even if the spell mastery ability applies, Exquisite Firecraft can be targeted by spells or abilities that would counter it. The part of their effect that would counter Exquisite Firecraft won’t do anything, but any other effects those spells or abilities may have will still happen, if applicable.

Check to see if there are two or more instant and/or sorcery cards in your graveyard as the spell resolves to determine whether the spell mastery ability applies. The spell itself won’t count because it’s still on the stack as you make this check.