Even in their crowning achievement - the cloud, they are a distant second to AWS and Amazon always brags that they run more Windows instances in AWS than Microsoft runs on Azure.
MS’s revenue is half that of Apple’s and they have lower profits. Heck, last quarter Apple made about the same as Microsoft even if you subtract iPhone revenue.
They missed out on mobile for sure, but it's not because of their focus on the enterprise or backwards compatibility, and you'll have a very hard time proving so. Also they haven't missed out on the web either, and neither can you prove that they did. Just because there is a bigger cloud provider doesn't mean that they 'missed out'. And there will be bigger fish to fry, new technologies are coming out every year.
Apple and Microsoft are in vastly different spaces. Apple focuses on consumer products, Microsoft makes its money from the enterprise. An Apples to orange comparison is not meaningful.
As far as mobile, Apple was able to take its much smaller less bloated OS, cut it down to a size that could fit on a device with 128MB of RAM and have for what at the time was a full featured web browser. Did you ever use IE on a Win CE device?
And are you forgetting that Microsoft was the dominant consumer operating platform before mobile? MS didn’t have any choice but to retreat to Enterprise.
So what “bigger technologies” do you see coming out then mobile? The smart phone already has an 80%+ worldwide penetration rate of adults.
They run windows at Google HQ and AWS but you don't see anyone saying Google and Amazon "missed out"