To my knowledge all modern DCs have out-of-band networks for this sort of thing that provide serial access to the BMC chip, nothing old school about that. Old school is having to submit a ticket to Jerry in the DC to walk the crash cart down to box 55AE, hook up a serial console, run diagnostics, and attach the output back to the ticket. You only have to deal with Jerry occasionally now, usually when the BMC or power rails fail.
There's more than a few people who've decided the security risk of full console capable bmc is not acceptable - and if other fail over systems are engineered appropriately, not necessary at all. BMC/IPMI intentionally disabled/not connected to any network.
Anecdotally I have seen a number of low cost x86-64 pseudo blade setups similar to open compute platform design stuff which have no oob. If a unit fails it's pulled entirely and put in a work queue for someone to repair.
