Supposedly All for One Impact Recoil quirk "enables All For One to completely reflect the impact of an attack back to the attacker". This seems to be the quirk used in season 3 episode 10 in the battle of All for One with All Might. If he can revert the impact of an attack back to the attacker, to use it all the time wouldn't turn the user invincible? Then why All for One doesnt use it all the time, does it have any flaws or drawbacks?
to completely reflect the impact
From where did you take this information? According to the Boku no Hero Academia Wikia the physical impact gets reversed, but not "completely reflected".
So, it wouldn't turn the user invincible, because the user is still to some degree affected by the attack (as written in Boku no Hero Academia Wikia):
However, this Quirk does not seem to cancel the impact completely
That is probably why All For One uses Gran Torino as a shield instead of taking the punch himself.