Not everything actually requires a GUI, obviously. But anything that requires configuration, especially for controlling a hardware device, should have a fully functional GUI. I know Linux is all about being in control, and users should not be afraid to use the command line, but if you have to learn another bespoke command syntax and the location and structure of the related configuration files just to get something basic to work then the developer has frankly half arsed it. Developers need to provide GUI's so that their software can be used by as many people as possible. GUI's use a common language that everyone understands (is something on or off, what numeric values are allowed, what do the options mean).
Every 12 to 18 months I make an effort to switch to Linux. Right now I'm using Archlinux, and it has been a successful trip so far, except my audio is screwed, I can't use my capture card at all, I had issues with my dual displays at the start, and the is no easy way to configure my AMD graphics card for over clocking or well anything basic at all.
I'm not looking for a windows clone, I love that I can choose different desktop environments and theme many of them to death. I even like the fact there are so many distros. Choice is a big part of linux, but there is clearly a desire to get more people moving away from Windows and until that path is 95% seamless most people just won't. Right now I think Linux is 75% to 85% seamless depending on the use case and distro but adding more GUI front ends would, imho, push that well into the 90% zone.
GUI is not a dirty word, it is what makes using a new OS possible for more people.
EDIT: Good conversation all. This is genuinely not intended to be a troll post, I just feel it is good to share experiences especially on the frustations that arise from move between OSes.
Believing that GUI is a common language is funny.
CLI is literally a common language as long as devs follow the actual rules. GUI? No. There are no rules for where configuration is. File->Settings? Maybe. Or maybe it's under Edit. Or maybe it's behind a gear symbol. You point out you like the variety of desktop environments but ignore that it's not easy to get something to look great in everything. It's like back in the day trying to get a website to look nice. It was either basic HTML that looked good in IE and Netscape (I know there were others, but let's be real) or you had something fancy that only worked in IE. So yeah, folks spend their valuable time on providing functionality instead of looking pretty. Sorry not sorry? Until more money goes towards those projects, you're going to be missing unnecessary bells and whistles. There's a reason Mac looks pretty. Money.
I will take new features, performance improvements, and bug fixes over adding a GUI every day of the week.
Devil's advocate:
ffmpegis not common language, it's an eldritch incantation beyond human comprehension.