To figure that out, we'd need to look deep into what's happening in the machine, down to counting cache misses, memory bandwidth usage (per channel), QPI link usage (because NUMA), and, maybe, even go down to the usage stats of the CPU execution units.
When they mention a lot of what was stored procedures has been moved to external web services, I get concerned they replaced memory and CPU occupancy with it waiting for network IO.
Assuming the poster Aussiepete80 is Australian I should point out that the much higher salaries in the US and the favorable E3 visa has largely brain drained Australia of their best and brightest. This guys army (dozens) of DBAs is likely the residual.
Predators here in Ireland are terrifying. The other day I was almost adopted into a family of feral cats.
Plus I would submit the reddit thread 'Biggest CPU for the Bad System' as evidence to my point. How could this person possibly think that 100s of CPU cores are the bottleneck and the solution is more CPU cores - how could the dozens of DBAs not figure it out - the amount of work that can be done in 100s of CPU cores is utterly insane and the fact that they didn't rule out obvious IOWait bottlenecks in their initial posts suggest that none of them know what they're doing. I guess they figured that Azure would take care of all of that.
The initial step would be to bring that computer in house and design that computer around the problem - Azure is not going to be open and honest about their bottlenecks. Last I checked Azure was big on their Network Attached Storage and Managed Disks which add quite a lot of latency and throughput bottlenecks compared to a PCIe 5.0 Enterprise SSD.
If you think there is a risk your database will grow to be enormous, it’s likely it’ll be the worst possible choice, with the possible exception of Oracle and DB2 on AIX (but, on the last two, at least you have fewer limits to scaling up).
Could also be a B-player hires C-players situation, with borderline incompetence trickling down from the C-level.
The reason for my brain drain statement is that people don't understand how pernicious the brain drain is in Australia. The Australian government believes that there isn't a net brain drain because more people with degrees immigrate than those emigrating. But people are not substitutable cogs and the very smart are very rare and it is the loss of those few very smart Australians to the US which is so devastating.