If we never replace things with better things, we'd be using superpowered DOS machines to this day. I don't get the "knowledge has to be discarded and then has to be replaced by different knowledge" argument if the new knowledge is of a better tool.
I'm not all in with systemd's ethos, but I don't see a significantly better tool around.
> 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.
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.
Modular designs are good, monolithic designs are bad. Dependencies are bad and so on. Lots of choices at the design level were made against fairly hard won knowledge on how to architect complex software systems. All these dependencies translate into 'all or nothing' and that is never a good thing in the software world. It's just another form of lock-in, something that the world of closed source software is good at and I'm quite sad to see it pollute the world of open source.
Edit: I suspect a lot of the pushback against systemd - mertited or not - is because a lot of people in charge of little parts of the bazaar have seen their pet projects cast aside by the major distros and taken over by the systemd devs. In a world where street cred is a big force in motivating people to contribute to open source being maintainer of 'x' where 'x' is part of each and every linux distro out there and then to see 'x' taken over by systemd in a fairly rough manner without any kind of co-operation between the old maintainers and the new kids on the block there are bound to be a lot of ruffled feathers. But that's not technology, that's just ego.