I didn't say it's rocket science, nor that it's impossible to do without having practical server experience, only that it's more difficult.
Take disks, for example. Most cloud-native devs I've worked with have no clue what IOPS are. If you saturate your disk, that's likely to cause knock-on effects like increased CPU utilization from IOWAIT, and since "CPU is high" is pretty easy to understand for anyone, the seemingly obvious solution is to get a bigger instance, which depending on the application, may inadvertently solve the problem. For RDBMS, a larger instance means a bigger buffer pool / shared buffers, which means fewer disk reads. Problem solved, even though actually solving the root cause would've cost 1/10th or less the cost of bumping up the entire instance.
