@ Hans 1
I do think the author knows a thing or two about IT, whereas your approach suffers from a lack of understanding of several very basic facts about the whole business.
The article is aimed at people/setups which are firmly rooted in a microsoft environment, with the inclusion of the possible existence of some very specific business-critical business apllications developed for and on this microsoft platform. It's acually pretty comprehensive for a quick overview.
Now the thing with open source, as it has been from the early beginnings, is how well it supports your existing infrastructure when/if you decide to switch, and how much of the needed knowledge is already in-house if you would implement it. Which usually amount to double negatives for most small companies, and as such is as much of a No-No as moving your entire business to the Cloud.
Switching "Offices" alone gives a bunch of headaches, besides retraining staff, because the Microsoft variety is so well integrated compared to the Libre flavour. This means that you'd need to go over all of your scripts, letterheads, shared spreadsheets, etc. etc. to find out what gets broken ( and oh boy.... things will get broken.. ) and fix them. If Libre supports whatever-you're-used-to-doing at all to begin with. Libre has come a long way and is quite good nowadays, but it still has some idiosyncracies that makes it necessary to upend some things which are "natural" and expected when you're used to working with the Microsoft line.
Server-wise you're dealing with something similar. Your staff is trained in using/maintaining Microsoft servers. With all their little foibles and workarounds, and ...stuff... They may or may not be versed in Linux/BSD flavours, but even if so, they're not getting paid to administer them. They're getting paid for keeping the microsoft servers running, and their training and inclination will reflect that. They also keep those legacy applicaations running, and will in general have a dim view of some new kid coming in wielding the "Open Source is da Bomb!" hammer. BOFH's look for suitable PFY's.. The ones that aren't tend to meet the same fate as Sales Drones and Bosses. They generally are not waiting for a year-long session of More Work, More Headaches, More Incompatibilities forcibly introduced into their lives. More so if they actually have looked at Open Source in the past and encountered the flag-waving, barricade-bashing Lintard crowd and other types of cellardwellers frequenting the Land of Support in Open Source land.
Admittedly, these hurdles can be overcome. Technical issues are just that, issues that can be solved by the competent, and Software, open source or proprietery, can be assessed purely on it's merit and business case, ignoring the activists and trolls. Which leaves the business case. Because you will have to shell out extra cash to get things done, even if you choose "free" open source software. You will either have to get the knowledge in-house and keep it there, which means hiring new personnel, or rather ...replacing... the personnel you work with, or buy a service contract with one of the business oriented open source solutions. Which for small companies means you have to boot people you actually know and/or do business with a different kind of devil that so far has an unproven track record.
Whichever way you look at it, it will cost you, as a business owner, a lot of time, effort, money, and in extreme cases some Unpleasant Conversations to switch to open source. As opposed to having your existing personnel ironing out the few differences while upgrading to the next version of the devil you know. It's really a no-brainer, since the total costs of migrating to open source are simply far greater than extending/migrating within the microsoft environment.
IT, for a modern business, has indeed become part of the backbone. And just because of that, business owners and managers have become very conservative in applying major surgery on it, lest they break the spine..