Former Scilab intern here:

Scilab development started from the same Fortran code Matlab did, around the same time; also it rarely attempts to copy Matlab syntax or behaviour. (I'm just saying it should be seen more as an alternative to Matlab, not a copy.)

I personally would tend to agree that developing in a general purpose language is better for most problems but an imperative math-oriented language that's simple to apprehend remains a large use-case for scholars and engineers. For that I feel that the rewrite of most of the code in the past few years has been a worthwhile endeavour.