I'm pretty sure most people sysadmin'ing their Linux servers are actually doing it with rented dedicated servers. TFA btw specifically mentions: "don't manage physical hardware". Big companies like Hetzner and OVH have hundreds of thousands of servers and they're not the only players in that space.
They don't take care of "everything" but they take care of hardware failure, redundant power sources, Internet connectivity, etc.
Just to give an idea: 200 EUR / month gets you an EPYC 3rd gen (Milan) with shitloads of cores and shitloads of ECC RAM and a fat bandwith.
And even then, it's not "dedicated server vs the cloud": you can have very well have a dedicated server and slap a CDN like CloudFlare on your webapp. It's not as if CloudFlare was somehow only available to people using an "entire cloud stack" (whatever that means). It's the same for cloud storage / cloud backups etc.
I guess my point is: being a sysadmin for your own server(s) doesn't imply owning your own hardware and it doesn't imply either "using zero cloud services".