Sure, if you ignore all the data to the contrary. Despite repeated assurances from the Linux Desktop community that it is "good enough" it still has almost no buy-in, even though it is free. Valve has taken on the herculean task of making Linux Desktop a viable platform for games, which have long been an excuse as to why there's so little adoption, and still there are very few takers. Microsoft has seemingly put a lot of effort into trying to kill the Windows Desktop, and still there is no traction.
Until the Linux Desktop community actually starts listening to what users and developers are saying about why they don't like the Linux Desktop, and start taking responsibility for its problems, it is unlikely it will ever be taken very seriously.
Wrt fragmentation: on Windows there's a confusing choice of multiple app frameworks with no clear roadmap as well, which is very frustrating to Windows developers: Win32/Winforms, WPF, UWP, etc. Most new desktop apps, even those by MS such as Skype Desktop and VS Code, are cross-platform and based on Electron.
Apple has recently ditched Open GL; what kind of message does that send to Mac OS app publishers regarding any long-time commitment to the Mac platform?
The situation on Linux has been like that for ages; it's not going to change unless you want to throw away all the apps there are (cf. https://xkcd.com/927/). And maybe Ubuntu's UI is a bit frugal and ugly compared to Mac OS, but it's working in a predictable and rational way, and no less unified than Windows. If you have an issue with it, you can change it the way you like, rather than expect others to do it for free.
Specially if we expect the users to pay for desktop software.
However laptops and 2-1 convertibles are also desktops.
Windows 10 is still less evasive than those Android devices on our pockets.
But the thing is, if you're making a large application, for Gnome for example, then you can't by default be confident that your application can work very well on other desktop environments like KDE or XFCE.
I think this is what the speaker have meant: Linux Desktops moves many responsibilities on to you (You need to test your app against for each desktop environment for example). And sometime, that many responsibilities can be troublesome (burden, to say the least).
This just isn't true. There are literally 40 different graphical environments available that can run X applications. If your target desktop has the required libraries for your app to work OR you have packaged them with your app it will work regardless of users desktop.