Yes, the only reason I cared for Linux in first place was that the POSIX support wasn't that good.
I am convinced that if POSIX subsystem was UNIX serious, GNU/Linux would never taken off on PC, and the whole would be divided between SGI, HP-UX, Solaris, Aix and Windows NT.
There were already better free options than Linux when Linux first started gaining traction.
The reason Linux grew in the 90s was because it was part of the hacker culture. Not because better options didn’t exist.
Kids liked the fact that Linux was a free-for-all, anything-goes, platform. It wasn’t stuffy like Unix and it wasn’t proprietary like Windows.
Then those kids grew up and became decision makers themselves. And we started to see Linux replace FreeBSD and commercial Unixes.
Which ones? BSD was tied in a lawsuit that left doubts on its future.
Minix was a toy OS for university teachings.
Coherent was commercial.
Nothing else was there on the PC market.