I like them in the sense that I think they are flavorful and well-used.
I do NOT like them enough to say "Every class and subclass option should have this additional layer of detail/built in flavor."
I am good with the big 4 having a "simple" option.
Then you have the "initial subclass classes": druid, paladin, ranger, illusionist, assassin, monk. [Bard and Barbarian, arguably, are tag-alongs, here]
Illusionist and assassin have already been shunted to -for lack of a better term- "1st tier" subclasses of their own.
The others -like the big 4- have some "simple/default/1st tier" subclass choices, that convey the "basic [or AD&D, really]" character archetype.
Having an option that adds that additional layer, a "subclass +1" if you will, makes for a nice/good differentiation from others of its base class. An arctic [Land] druid will be/play differently than a coastal [Land] druid than a [rather default] woodland [Land] druid.
The Totem barbarian is slightly different options, kind of a "2nd tier" subclass (as its the only one), allowing you to switch the benefits of your secondary choice between levels. Ranger's Hunter archetype had elements, though not as flexible, of this as well -choose one of these at level x, choose something else at level y, etc...- but you were still a "Hunter Ranger." And, in "un-/semi-official" terms, I recall at least one UA incarnation of the Shaman that followed this kind of structure, also.
The warlock, then is -again, making up terms here- offers a variation on the "3rd tier" subclass, distinct from the 2nd tiered ones, in addition to the most mechanically complex sort of "base class."
So now, we have the character options of:
Base + Sub.
Base + Sub. + 1 that does not change, all features are the same regardless of what "1" is.
Base + Sub +1 that does not change, some features offer choices/change at varying levels.
Base + Sub. +2 (+1 that does not change, and all features are DIFFERENT depending on what "1" is, AND +1 that also does not change, but grants distinct features depending on what this second "1" is at varying levels).
I think that is more than enough variety for a given game. Perhaps even too much/a little unnecessary complexity.
So, yes. I like them. But I don't need to see more of it. New constructs of character/class archetypes need not include "Base + Subclass +1 (or more)" more than, say, once in 10 or so subclass/archetype options.