What on earth are you talking about - this article is talking about 32 bit OS/2, not the 1.x 16 bit releases.
OS/2 has never had a separately sold CLI and GUI. OS/2 1.0 had no GUI. Technically you can boot OS/2 without PM if you want a text only boot, but that's usually only used in embedded systems.
OS/2 up to 2.11 didn't include networking by default. v3 had 'connect' options with networking included. v4 had only one edition, with networking included. The Netware client was free.
The price was not ludicrously expensive. I bought the releases, as a student.
OS/2's DOS mode was exceptionally good - in the 32 bit release, that this article is talking about. The 16 bit versions of OS/2 had issues with DOS compatibility, because they ran in 80286 protected mode.
At the time OS/2 2.x onwards was around, there absolutely were graphics/memory/etc APIs. It's only for DOS games it was an issue.
There are several reasons OS/2 failed :
Between 92-95 (OS/2 2.0 to Warp v3) it was a much better OS. However, It's All About The Apps, Stupid. OS/2 never got the app coverage, and the compatibility with DOS/Windows was superb.
So, you have a choice between a relatively expensive OS/2 app, which fewer people have used, with a different file format. Alternatively, buy the Windows app and run it under OS/2. If the app dies, it doesn't take down OS/2.
Describe was technically an excellent word processor, and the output quality was fantastic. Unfortunately it was simply much less usable than Ami Pro under Windows, and Ami Pro for OS/2 was a deeply shitty port.
Mesa was an awesome spreadsheet, but it wasn't Lotus 1-2-3, or Excel - the de facto standards. Still, if you wanted to throw 300,000 rows in your spreadsheet it'd work fine - unlike Excel which took into the millennium to fix that.
Generally you paid more for higher quality functionality, but less of it. That just wasn't what the user base would accept, but is the reality of a smaller user base. IBM was not good at funding companies to develop software.
Second, the install routine sucked. Microsoft spent a lot more time ensuring the install worked. OS/2's install has always been sub-par, and the hardware support meant that to run it successfully you selected the machine based on OS/2 support, not bunging it on a random PC.
Third, Microsoft played dirty, and for the non 'for Windows' (fullpack) versions of OS/2, IBM was paying MS a Windows license cost for each copy of OS/2 sold. This also heavily affected bundling with machines (it wasn't, except by IBM) so the install quality became more critical.
Fourth, IBM lost the plot with Workplace OS, thinking they could regain the market with a PowerPC infrastructure. That's the point at which OS/2 decisively lost - the emphasis on what to develop was wrong.
I was a big OS/2 fan, but must accept that NT was simply a better OS. It was designed well from the start, from scratch. OS/2 wasn't - for 2.x onwards, it still had 1.x code (the 32 bit GDI came in a 2.x service pack, 32 bit windowing only came in v3), was relentlessly single user and never addressed some extremely irritating long term issues such as the synchronous input queue.
None of the above mattered for a while. If IBM had junked Workplace OS and re-architected the necessary parts OS/2 might have survived longer. However, It's Still All About The Apps. Apple were suffering at the time, and one of the critical reasons they returned to success was an agreement to release a new version of MS Office for OS X.
Seeing as WordPerfect and Wordstar royally fucked up their Windows releases, and Lotus never gained traction (pity, I greatly preferred their products) the market shifted to Microsoft apps. That needed an MS OS, and relying on running a compatibility layer for your competitor's products is a losing strategy.