Google's big advantage is that their core product has fundamental value (search and by proxy: ads) and their secondary products are such loss-leaders that outcompeting those freebies (Google office suite, Gmail, maps, YT, chrome, ml tooling) is where the real difficulty comes in. But building a core-search competitor is far easier than competition with Apple or Msft's core products. Google has a lot more scaffolding that FB, but they too have a single point of failure. A sea-change (like Mapreduce, pagerank, the smartphone) can see them collapse swiftly.
On the other hand, enterprise / feature-checklist companies lie in a stable equilibrium. You can't really beat them unless you invest a similar amount of resources into it. And even if you defeat them, they'll catch up to you in time if they're run at similar levels of competency and can throw a ton money money at it. Microsoft and Apple are exactly that. It's like trying to start a Boeing or Nvidia competitor. You better at least be at Airbus's or AMD's level before even trying to compete against boeing.
Microsoft's weakness is best displayed by Adpbe's acquisition of Figma. If Microsoft is run in a similarly predatory manner and a competitor gets 10 free years to catch up on 1 feature while you continuously fail to innovate, then you feel a mild threat, at which point you can simply outbid and acquire them. That shows how remarkably comfortable of a position Adobe is in, and Microsft and Apple sit a couple of orders of magnitude above that.
