I honestly think its laughable aggronant to rule out starships and FTL with our current understanding of physics. We know, for certain, that our understanding of the universe's rules is fundamentally flawed; general relativity and quantum mechanics simply don't mix, and we have two "Accurate" theories that describe different scales of the universe in fundamentally different ways. As such, I think it silly to assume what we currently know about physics is the limit of what is possible.