Without creative destruction in software, there is no Linux, there is no GCC. So no Apple macOS, all PC's run Windows, and likely there is no iOS/iPhone.
Microsoft would also [1] own the internet. Their browser IE would be the only significant consumer share, there would be no Mozilla, no open source browser. So no incentive to open the browser up to plugins. Microsoft would hold all the information on consumer browsing habits. Would they permit other search engines? Unlikely if there is no antitrust regulation compelling them to do so.
But that was then. I think your premise is, we more or less have all the software technology we need why do more, unless it comes from an incumbent, in the form of incremental improvements? Why shouldn't Apple, Google, Microsoft shut down their app stores a little more? Keep the development in-house. What's the point of allowing this creative destruction from 3rd parties? More and more, we only get these increasingly tired, corporate innovations. Fewer ports on computers in the name of locking down devices to make them less 'hackable', more restrictions on these OS that increasingly feel like sandboxes, because why bother giving users the unfettered ability to create stuff, it just allows more creative destruction. Why should corporations knock it out of the park when they can just suppress upstarts with unfair competition?
By the way, antitrust regulation also prevents [2] Apple, Google, Adobe etc suppressing developer salaries. Remember antitrust law also shares incentives and motivation, to encourage progress.
But the better question is what is the future without without creative destruction, without shared incentives and competition? We have the answer in thousands of years of monarchies. Monarchies are a stagnant form of human development, they have no incentivize to upset their current order so they constantly suppress change. We don't celebrate this ancient monarchy or that one, like we do federated political systems. Compare the cultural developments in ancient Greece's federated city states vs surrounding empires. Or the Roman Empire, when it was ruled by the Senate, before emperors ran it into the ground. Or the Gutenberg Press, that brought printing to the European states where publishers were incentivized by profit, compared to dynastic China that developed the technology hundreds of years before, which helped trigger the Renaissance. Or Britain after the Glorious Revolution broke the monarchy's monopolies and led to the Industrial Age. Or the Jamestown settlement after it began profit sharing to motivate the colonists, in the face of failure, which directly lead to the political institutions which created the United States of America. Without power sharing, all civilizations degrade into inheritance systems, where opportunity is few and far between, unless you go rogue.
[1] https://www.theverge.com/2018/9/6/17827042/antitrust-1990s-m...
[2] https://www.justice.gov/atr/case-document/final-judgment-0