@yaakov not necessarily. ojAlgo has been around since 2003 and while it isn't CPLEX (which it does support on a side note), it's a mature, reputable, and performant library. For all the performance criticism Java gets, it does provide some immediate wins until Kotlin/Native takes off.
I think what a lot of people overlook is Kotlin doesn't strive to be phenomenal at <some niche task> like linear programming. It tries to balance pragmatism at being a general purpose programming language like Python. If you want to use a language that only does one thing well, you certainly can (
https://ampl.com/).
On a side note, it surprises me when I see Groovy enthusiasts criticize Kotlin. People can have the most interesting biases.