Jobs created the initial problem by undermining the Apple 2 GS.
Apple could have launched in iPhone like product years ahead of when they did if they kept that branch of the company afloat. That would have been a real 'visionary' move. Instead, they were forced to differentiate themselves in a crowded marketplace by emphasizing little design flourishes and style.
Job's only real contribution is managing to gaslight (a.k.a, his "reality distortion field") the entire industry into thinking he had any real insight or ability beyond that of a typical middle manager with a cluster-b personality disorder.
We can't speculate on what a Apple Prime would have done without Jobs. But we do know that his single mindedness about making arbitrary changes cost them several years in the 80s and led to the slump in to the 90s.
It would have been exposed as being a dead end with no backwards compatibility. The GS was essentially a completely different architecture from its predecessors anyway. Compatibility was maintained with the Mega2 chip. Apple wouldn't have been stuck for a couple of years with barely any software on their "flagship" product.
The GS would have killed the Macintosh if they raised the clock speed, gave it some higher video resolution modes, and developed something like the Macintosh Toolbox in ROM for it.