I can't speak to the merits (or lack thereof) of string theory. That's well beyond my physics knowledge. It must however be daunting to be a theoretical physicist right now. It seems like the field has been in a standstill for years. The advances in the 20th century were just eye-watering. The Standard Model is a mixed bag of stunningly accurate prediction (eg electron monopole moment [1]) vs the wildly inaccurate (e…
The second link reignited my bias for Zeldovich as not having sufficient public recognition. I previously knew him as the originator of the idea of Hawking radiation (he predicted it around Kerr black holes, and told Hawking about that), but it looks like he also had major contributions to both the Soviet nuclear project and the vacuum energy problem (as you say still unsolved).