I am sorry to hear this. Anything that reduces diversity reduces the resilience of an ecosystem. Unfortunately, it seems that the niche OI was aimed at failed to attract a critical mass and the commercial variants of Illumos didn't see any benefit in supporting OI.
Alasdair is right that GNU/Linux is a monoculture - just because it's OSS doesn't prevent this.
Some of this is active antagonism to anything other than Linux. Witness the attitude of MongoDB in the link Alasdair posted: "you're not using Linux, we don't want to hear from you". And cases where Linux developers have deleted all the code not needed for Linux on previously portable code.
This is fostered by GNU's "extend-and-embrace" approach - lots of seemingly nice but non-standard extensions that lock you into GNU. Whether intentionally or not, lots of OSS developers write "C" code that can only be compiled by gcc and scripts beginning "#!/bin/sh" that fail on POSIX shells. Libtool and autotools are classic double- speak - they claim to promote portability but actually do the opposite - the code might be portable but autotools and libtool still endeavour to make building the code as painful as possible unless you have a GNU toolchain (preferably on Linux).