The IIGS was, essentially, a '816 Macintosh that happened to have hardware compatibility with the legacy Apple ][ series.
Software wise, it was bipolar trying to juxtapose between the IIGS desktop software and the evolutionary ProDOS environment. (Which is a gross generalization, as ProDOS was part and parcel to the desktop environ).
But the IIGS software was a second stab at what the Mac had already become, but a little better thought out with lessons learned from the Mac. Not quite a second generation Macintosh.
@Singletona point is the belief about how the IIGS was hamstrung so as not to compete with the Mac. The '816 was clocked at only 2.8MHz. In theory it could have been clocked faster (I believe that there were accelerator cards to that affect).
In that regard, at the time, the IIGS could have been a real competitor to the Mac as a faster COLOR(!!) Macintosh. I’ll let other extol the virtues and clock timing of a '816 vs a 68K.
Whether there was much future for it, is difficult to say since the '816 effectively peaked at that point. Was the Apple market enough to drive development of the chip any farther in contrast to what Motorola was doing at the time with its broader application base for the 68K family.
The IIGS was some complicated hardware with it’s legacy capabilities. A “pure” '816, with a better clock rate (Spec goes to 14Mhz, but many have pushed it to 20Mhz), and color display (the IIGS did not have sprites et al) would be an interesting machine.