Existence doesn't mean much in times of quantitative easing; pick your favorite punching bag company in recent memory that is still extant. If you don't understand the economic situation backing all this it's hard to discuss your rebuttal further so we need to checkpoint there before I invest any time on more responses.

The issue is largely orthogonal to my own skillset because one needs to only view quality regressions in order to assert my point, not be the cause or hero of them (ain't philosophy generous?!). The times a 2 year experience system operator could go in and wreck havoc on a mainframe operation were not particularly common and the standards and practices (i.e. airgapped backups on tape, geographically dispersed sysplex etc) ensured business continuity were generally planned right in from the initial purchase order with the vendors' help once upon a time. In this decade people can and did launch massive financial exchanges on mongodb when it had serve and well known issues.

Good enough according to whom? Inevitably there's always some unpatched server somewhere on the network someone forgot about that let hackers access data for millions of customers.