Unfortunately for databases under a heavy load it's out of the question.

You can have a server pegged at 100% CPU waiting on disk with spinning disks, and without changing anything else on the server RAM or CPU, and just replacing the drives with SSD you can quickly see that load drop down to 10%.

Random reads are an order of magnitude slower so for fast access there's a notable difference. Still a role for hard drives with sequential reads/writes, such as the regular backups they should have been taking! Slower in all areas but cheaper for the same space.

Spinning hard drives are the tape drives of the modern era. Boot, logs, backups, but no databases.