Agreed. But I don't think Smith cares about relevance, he likes to tell his stories. I used to listen to his podcast where he talked about if podcasting had been a thing 20 years ago he probably would have just done that. I think the bug crept up again like it has with others even before these two.
As far as legacy goes. Smith I don't think will ever be to T's level, but I think he's secured himself as an indie darling.
Tarantino is unique for two reasons; He is shameless in his admission that he makes movies about movies. That is, his references & sensibility are largely stolen, however this very style is what makes his films instantly recognizable.
Second, he knows his limits, his scruples. He knows he cannot bend to corporate whims, he can never be a "hollywood director" and because of this he has many more obstacles and barriers to his creative expression. The only real obstacle (other than $) IMO is his own self-indulgence, and his own sense of thematic satruation. By that I mean; sticking to what Tarantino does best, while walking the line between his strengths and being a parody of himself. (Which he has come dangerously close to)