This is Smolin, making his usual, and valid, criticisms of modern physics. Smolin's basic complaint is that there is no experimental evidence for string theory. The math is pretty, and a whole generation of physicists have worked on it, but nothing is experimentally testable. Everything is too small or at too high an energy level. A practical implication is that it doesn't lead to any technology.
Smolin also doesn't like many-worlds, because it talks about unreachable regions. This he considers too speculative. There's a basic problem in quantum mechanics, which leads to Schroedinger's Cat, the Copenhagen Interpretation, and, in the end, many-worlds.[1]
Physics has been stuck on this problem for almost a century now. Philosophy won't help.
Smolin also doesn't like many-worlds, because it talks about unreachable regions. This he considers too speculative. There's a basic problem in quantum mechanics, which leads to Schroedinger's Cat, the Copenhagen Interpretation, and, in the end, many-worlds.[1]
Physics has been stuck on this problem for almost a century now. Philosophy won't help.
[1] https://en.wikipedia.org/wiki/Copenhagen_interpretation