LTSC: What is it, and when should it be used?

Serpentbane, but that is the point. 

One of the main reasons why organizations chose LTSC in the first place is to NOT get the "new features" you were talking about. 
Microsoft made it very hard on Windows 10 to get rid of things the Organization does not want - things like setting file associations etc. needs a lot of workarounds to make it work because it is obvious Microsoft does not care about Admins anymore. 

This was much better on LTSB/C, as a lot of the stuff that people want gone (Store, UWP Apps, Edge, Cortana... and their file associations etc) were not there to begin with, so they didn't need to be disabled/hacked out/worked around, etc. 

Also, we deploy our devices for a four year cycle, and by using LTSC, we could just deploy these devices and keep them on one version for the entire Lifecycle - no changes, no stuff breaking. 

It is the little things that happen with the Windows 10 updates - defaults get changed, they add new icons to the task bar (I had a ton of support calls when the unwanted "Mail" App was auto-pinned to the taskbar with upgrades), the interface is changing constantly (looking at you, Windows Search) ... people do not want that. Neither do we want that as Admins. You might like the "new Features", I  just see "more crap I have to disable/remove". 

Also, people HATE when the upgrades arrive. They take a long time, happen when they want to shutdown/quickly reboot their machine and hinder then from going home (99% Laptops), and are a hassle. And I have trouble forcing my users to have a single reboot a month as it is (IT had to override Management on that one). 

Just remember that back on any other version of Windows, you only had to worry about deploying to a device once, have it auto-configured by whatever scripts you built, and only worry about the monthly updates.

Now, with every new Windows 10 version I have to verify that my scripts still work (PSA: often they get broken by changes from Microsoft), I have to verify my Drivers and Software all still work, figure out where Microsoft changed the presets set by users in the upgrade process, where they added unwanted "features" and GUI elements, update my GPOs ... Administering Windows 10 devices to a level that my Organization wants (not to a level that Microsoft deems "suitable") creates about five times as much work as Windows 7 or Windows XP did before. 

I know, a lot of people seem to like Edge, Cortana, etc.. but we don't. We don't want them, we don't need them. We do not need UWP, we do not need the Store, we do not need another Browser or Security Software. We just want Devices for our Lifecycle that behave consistently from one day to another, and GUI changes are not consistency. 

It was hard enough to figure out how to turn most of the annoyances on Windows 10 off, but to have to do it repeatedly every 6-12 months is just.. argh. 

Just as an anecdote, I had a script (why do I need a script for this) that unpinned Edge from the Task bar - as it was not a normal icon but some system functionality deeply hidden that put it there. In the end, it worked and the icon was gone - and it worked fine in 1809 or older. When we moved to 1903, it still worked that it unpinned the icon - but now users couldn't pin stuff to the taskbar anymore, as it was forgetting the pins after logout.  Why is simple stuff like that so hard... 

I am currently moving all our devices up to 1903, and when that is done, to 1909...and we expect to stay on that version as long as support runs out (30 Months)... and until then, hopefully Microsoft will have revised their update model, as they seem to begin to realize that 6 Months is way too often in corporate land. 

in an Ideal world, there would not be two, but three Tiers to Windows 10:

SAC, the same as before, 18-30 Months support.

LTSC: The same as before, 10 Years support.

LTS-Business: New Channel, no new feature updates, released every ~3-4 Years, with an equivalent support period of ~5 Years. Create one Year of overlap from one release to the next.