Maybe there is no excuse, but literally every company I've worked for (including Fortune 500s) has been missing at least one item from your list. So "industry best practice" means committing less time and money than it would take to implement all those things properly (rightly or wrongly) and you need to triage and prioritise.
You see this "authN/authZ above all else" line of thinking in Google's security design [0], with their ubiquitous login wall. For their employees, that login wall has extra hardening - you can't do regular password resets, and you need to possess a physical security key (which acts basically as a scaled-down single-purpose HSM) and pass a suite of posture checks on the device (proportional to the sensitivity of the protected resource) to pass through it.
Then they put this login wall in front of everything, even internal services, and that tends to be OK because the system "fails closed," and the only way to access their protected resources is via physical safe rooms deep in the Google offices in which elevated privileges may be obtained.
Putting all your systems on the Internet forces you to get the incentive structure right, and that can be useful in companies where "private networks" can serve as justification to weaken security - if your login page is Internet-exposed, then you simply have no choice but to make it strong enough to withstand the chaos of the Internet. There's significant merit in that.
[0]: https://sre.google/books/building-secure-reliable-systems/