I welcome you to start your next hot startup in 2017 using Swing/Java instead of React/React Native/Node/Ruby/Python/Go/Rust/C++ etc. The merits of the stack are determined by both intrinsic factors and the market. Ignoring the market (remember Palantir is hiring in SV / Palo Alto) you risk alienating potential hires and current employees. [1] Another great example is EHR/EMR market with Mumps etc.
[1] https://www.quora.com/Why-does-Palantir-use-Java