Actually the things you are saying are factually inaccurate on a legal level, so lemme just slide some U.S. copyright law in the door here.
Fanfiction and fanart are a category of creative output that is generally protected by the law under the "Fair Use" doctrine of U.S. copyright law. This doctrine maintains that artists may create derivative and transformational works related to copyrighted material so long as these derivative works are not intended to "supersede or substitute" the original work and sufficiently transformational as to not be mistaken for a creation of the original copyright holder. As fanartists and fan writers have no intention or even remotely a chance of superseding or substituting their work for the original copyrighted content that inspired them, fanfiction and fanart by law are not stealing. To characterize the act of simply creating fanart and fanfiction as theft is factually false.
The selling of fanart is a grey area but does not remotely constitute the level of hypocrisy you are suggesting. Part of the Fair Use doctrine mandates that, in deciding whether something is "fair use" or not, the nature of a transformational work must be examined to determine whether it has a non-profit or commercial intent. However, even having a commercial intent does not rule out something being labelled fair use. Multiple factors weigh into the legal decision to determine whether or not a transformational work (i.e. fanart or fanfiction) meets the Fair Use criteria, including the work's degree of transformation from the original copyrighted content, the intention of the transformational work (i.e. to replace the original or not), and the potential for the transformational work to damage the profit-making capability of the original copyrighted work. Furthermore, there is no singular coherent international copyright law, so even if a work is protected in its home country, it may not be protected at all in other countries across the globe.
This is why many, many people are able to sell fanart without any corporate backlash--because the burden of proof is on the prosecution in these cases to prove that the fan work would have had serious impact on the original creator; a standard which few cases so far have been sufficiently able to prove. There are, however, numerous cases in which U.S. law has come down in favor if the commercial sale and reproduction of derivative works, such as parody novels and films, novels published in the extended universes of other series, and derivative products like companies that make Alice in Wonderland themed items with obvious homage to the Disney version of the film.
In short, fanfiction and fanart are not, legally, stealing of concept or design; nor is it even inherently against the law to profit off the fanart you create.
You know what is inherently against the law though? The seizure and reproduction of original copyrighted material without any degree of transformation. That whole "Nobody gets hurt when I upload someone else's art on my social media and claim I drew it?" That's called intellectual property theft, and it's a crime.
The critical difference here is the act of creation. A fanartist or fan writer creates something of his or her own that just happens to be inspired by the concepts and designs of another creator. They do not trace, copy-and-paste, or in any way claim that the concepts or designs utilized in the works are their own original designs. They transform and derive new works from existing works, but a new work is still being created.
An art thief simply takes a work from someone else and uploads it for their own personal gain (whether monetary or simply for attention) without transforming the original work in any meaningful way. They take, wholesale, the work of the original artist and claim it as their own. There is no new work being created--just one work being stolen and republished under a new "artist's" name.
U.S. copyright law sees a clear difference between these things. So should you.
(By the way, to make this remotely relevant to the OP: I'll just echo what others have said--it's not the commissions that are the issue, especially if you're only drawing people's original characters and not FFXIV's iconic NPCs; it's the advertising through the game that you should avoid.)