Just because Apple doesn’t satisfy your particular need doesn’t mean they should.Apple is supposed to be big and powerful (and courageous ?) enough to create a market but their focus is elsewhere, probably just in looks and money.
MacBook+Mac Mini+iMac+MacPro is not a line of products that can cover all needs and it certainly doesn't work for me, and, believe it or not, however weak/naive/sheepish the user and customer base is in this era, it won't work for Apple as well. They'd better undermine and limit macOS even more so that future users won't have any choice but using iPhones and consuming media.
If you describe your niche machine requirements and what you’re willing to pay, there are several here who can (probably) tell you exactly why Apple doesn’t make what you want.