I'm watching what happens when enterprise architecture is done badly, right now. I'm currently assisting a huge agency that is a mish-mash of smaller agencies. Multiple clouds, several data centres, hundreds (if not thousands!) of "apps" and servers. Every combination of bare metal, VMs, and cloud IaaS, PaaS, and SaaS. Much of it overlapping or redundant functionality.
It's an unmitigated clusterfuck: A nightmare tangle of interdependencies, band-aids, duplicated systems, inconsistent DR, non-existent DR, partial HA, and on and on.
If you've ever seen a "spaghetti base" in Factorio, it's like that, but as if a hundred players had been building one for a decade. Not just spaghetti, but multiple interwoven styles of spaghetti.
It's hard to explain to someone who hasn't seen it. Recently, someone upgraded a Layer 7 load balancer in a legacy data centre and broke an application in an unrelated Public Cloud because someone hard coded a HOSTS entry for the internal certificate CRL distribution point. Why was a cloud service using legacy internal PKI? Reasons. Why did it need a HOSTS entry? More stupid reasons.
The technical details don't matter, of course. The moral of the story is that because they don't have a good EA at the helm, they're still adding to the spaghetti.
I'm watching this unfold in slow motion. Layers of new stuff just draped over the existing garbage. No uplift. No clean-up. Nothing ever turned off. Just buried under new strata, slowly fossilising.
It's fantastic yet horrifying to watch, like a slow motion shipwreck.