> Mathematica user since 1988: i think it, in retrospect, might be great that it’s proprietary, in that it dampens its likelihood of trend-driven over commitment and resulting irrelevance.

I think that's not really true. It's not that Mathematica isn't trend-driven, just that it's responsive to trends more or less to the extent that Wolfram (company or person) is, rather than to the extent that the entire developer community is. Depending on how you use it, you may or may not like its embrace of new trends; while I've occasionally been glad it can do $CoolThing, I have also wondered sometimes why my Mathematica install needed to grow from, at some point in the single-digit versions where it was perfectly useful, a few hundred megabytes to now nearly 9 GB.