What issue do you have with the use of RecursiveFactorization.jl in DifferentialEquations.jl? I can't think of a maturity issue so I'm curious what you have found, or whether this comment isn't grounded in specifics.
Did my original post even mention RecursiveFactorization.jl or DifferentialEquations.jl? (or is this an implicit package promotion? I do not have issues with them anyway, perhaps great work, have not used them...) Regarding your second point, let's see if the language and its various package APIs remain stable, actively maintained, and backward-compatible just ten years from now, let alone 3 quarters of a century. Such issues do not become visible right away or overnight. I am not against the language, just stating the fact that it has yet to pass the test of time.