That's not my recollection of OS/2 3.0... It was snappy on contemporary hardware and 16MB memory.
But OS/2 was always sensitive to available RAM, and IBM liked to understate its memory requirements. (They pretended that OS/2 2.0 could run on 4MB because they had promised it years earlier. But it was really unusable on only four megs.) Maybe that was the issue?
I don't remember how much I had, but I think the "contemporary" is the issue. It really needed up to date hardware and most people didn't spend a lot on computers in those days so it would usually have been a year or some old.
And yeah I'm sure I didn't have a ton of ram, I don't remember how much though. I was only a poor student (but as a computer science student I already had a lot more than most people I knew).
But if someone just went home with a CDROM and installed it, it usually would not end well, this was part of the problem. I knew some enthusiasts that loved it but they did invest specifically to run it. That's just not great for an OS that still has to prove itself.