Linux

I have never bought the idea that free/libre SW in general is just not as easy, including GNU+Linux. I'll leave out open source initially, and come back to it later, not because it doesn't experience the same, but because corporate wide it doesn't suffer the same fate. And linux itself is one of the most widely used kernel if not the most, it happens similarly to openssl, and so many other open source components. So I see no issue with linux adoption, I can't think of any kernel more adopted than linux...

To me what has really affected free/libre SW is the monopolistic abuse of the corporations, plus their ambitions, and how in Today's world, they have created the illusion that being a technologist is the same as being a technology consumer, which gets into the hearts of governments and education systems (more hurting, public education systems). Let me try some practical examples:

• Educations systems translate the need to educate students about technology into making them familiar with MS different SW, like the windows OS, MS outlook, MS office, MS project, MS visio. Even on the higher levels of education, colleges and universities prefer to use matlab over octave for example, even for just matrix operations scripting. Office covers spread sheets BTW, so people specialized on accounting know excel, but no other spread sheet.
• On public education systems, where one would be inclined to think it might get more interest on developing the expertise to not depend on proprietary SW only, it's where corporate reach deeper offering "cheap" educational licences.
• From the prior two keep in mind that educational licenses from proprietary SW usually means future professional and people depending on proprietary SW in general. They are meant not to educate, but rather generate the future dependent population.
• Governments, whether local or nation wide, instead of adhering to open standards, for any kind of form submission, and even further to adhere to use of free and open source SW, to build the technical and competency expertise required to have a criteria about different technologies, about SW, infrastructure, DBs, and so, they prefer to require citizens to use non free or open source SW to create required forms, and prefer to pay for SW solutions which totally lock in the entire solution, usually coming from big corps, or other companies actually making use of SW and technologies coming from big corps.
• In their effort to discredit free/libre SW, the idea that the fundamental principles behind free/libre SW hurt the SW industry, or that are irrelevant to Today's world or even worse than that, there were claims that the GPLed kernel was a great threat and GPLed SW a cancer. Now that open source usage has totally overcome free/libre SW, there are no such claims, but the damage is done. There's nothing wrong with people wanting some compensation from corps, when developing SW, and thus not using free/libre licenses like GPL-3+ or AGPL, but in the end that eventually might hurt the users rights protected by such licenses, which such corps don't really care that much (their profit has higher priority for sure), and experience shows that just because SW is licensed open source doesn't guarantee any compensation for the development whatsoever, so if volunteering SW, doing so as open source is not even close to get every developer a decent income out of their contributions. Well, except for the big corps backed SW, linux included, but that's not the majority of open source SW.
• The discredit of free/libre SW, which allowed the eventual creation of open source, is such that the banning of individuals ends up being an attack to the organizations behind it and even their principles and motivation.
• Moving away from the free/libre SW observations, even now with open source, from the big corps, which barely compensate the open source developers, complain about the open source supply chain, campaigning against not well maintained SW and such, there's the famous image of a complex and heavy structure depending on a weak and deficient leg. Whatever truth around that figure, it of course hides the overall picture of the developer of such leg not ever being compensated (not to mention paid) for his library or SW component, and perhaps that's one of the reasons the project got even abandoned, but now it's easy to blame such situation when talking about FOSS in general.

Paid SW might be more intuitive to use at times, I can understand that. There are paid developers making the UIs more intuitive and attractive, in the end it needs to be bought or massively consumed to get earning through its use. But if you look deeper, perhaps it's not just that free/libre or open alternatives are non intuitive at all, perhaps people gets used to that UI when attending basic or high school, or college/university. Perhaps even when exposed to mobile devices even when they can barely walk. Everything else, different in nature, will look alien to the future "technologists"...

On a sad (lacking hope) note, I don't think there's any indicator of things changing. My only hope is changes in educational systems, which are nowhere happening, and not the parents, as mentioned they are already convinced that using google, ms, apple, oracle or whatever prepare their kids for the future and will make them the technologists of the future.

On a funny note, I would answer the motivating question with: Linux is so good that it's actually most probably the most used kernel world wide, :)