I've had computers since the KIM-1 and the TRS-80 were around so I'm well aware of the world of personal computing before the PC.
That also makes me well aware of how much a fully decked out computer cost before IBM released a hardware spec that allowed companies to compete and the vast economies of scale this involved brought prices down to where mere mortals like myself could afford very powerful machines. Unlike the various 8 bit offerings of the time, which were relatively expensive for the computing power and storage options they provided.
Even though the initial PCs were expensive and anemic and did not even have the same capacities as many other machines aimed at the home market of the time it had staying power because of IBM's formidable manufacturing and marketing capabilities and Microsoft made it useful enough that non-technical users would dare to make the jump. Tandy/Radio Shack tried - and to some extent succeeded - to do this too with their TRS-80 models. Competition by the clone builders then did the rest.
So I'm sure there would have been a 'computing scene' without Microsoft and IBM, and it likely would have been an interesting one. But the machine under my desk would likely not have existed in that world, other than maybe as manufactured by DEC, Apollo, SGI or some other player of those days and it would have been marketed as a scientific workstation and cost North of $10K instead of 10% of that.
General purpose computing for the masses rode in on the back of economies of scale that IBM and Microsoft enabled.
(And trust me on this: I'm not exactly a Microsoft fan but that bit they did actually made the world a better place.)