Sadly I have to report what you state is possible, but not plausible in today's modern heterogenous enterprise.
If I had a static environment with no new software or business processes, then NO PROBLEM. I can lock it down in every kinda way and it stays locked down to a known baseline.
Add to that new biz processes and now I have interconnection internally and externally which make detection and prevention difficult. Things are much more difficult now.
Add to that new software, ever changing dev env, OS updates, firmware updates, software version updates, dev env dependency updates, now you're talking near impossible to keep up.
And that's the state we're in today. There are some generic mostly effective controls that if implemented correctly can stop most advanced attackers (the so called "20 security controls") https://www.yumpu.com/en/document/read/6582321/20-critical-s...
But even in spite of that, any major nation state had an arsenal of "capabilities" that allow them to dominate most cyber warfare area of operations in the civilian sector. US can do it, UK, Israel, China, Russia, probably even India and others!
Against nation states, there is no stopping nation states in the civ sector, despite what every F500 company's CSO wants you to believe.....sad but true.