All of the servers I manage except for a few legacy ones are SSDs by now, for the simple reason that they are cheaper to operate at this point:
They consume less energy, and while their price per GB is high, their IOPS per GB is high enough that we can get away with far fewer replicas of each item of data and still get good enough performance.
I can't afford not to use SSDs in every new server we provision.
Not using SSDs in your servers today means you're behind the curve except in certain niches where performance doesn't matter but sheer storage volume does. That too is set to change within the next couple of years with current rates of cost reductions.
There are niches, such as long term archival, backups, etc. where disks may still be competitive, but even those are rapidly being eroded.
For things like web servers or database servers, I'll never provision another machine without SSDs.
> when disks were mechanical
DISKS are STILL mechanical. They will always be. That is why it's called a disk. You thinking is limited to fancy laptops and not considering enterprise servers.
> If we never replace things with better things
Better? That is far too strong. Things are not always better but making certain use cases easier. That does not mean it's better. Systemd has nice features, indeed; but it's also limiting in terms of losing the capabilities of full blown shell script. Sometimes this latter is very handy.
Edit: Downvote? Nice. Try commenting instead.