I maintain that the subclass system should be condensed and reorganized to make a little more sense (to me). I think that
I reject that position, and renounce the clear demonic influence of Grazzt that leads you to advocate it...
.....
jokes aside: I disagree...strenuously!
I find the tripartite structure of a character: Class/Subclass/Background(including Race here) is both broadly modular and capable of being further refined and defined through use of Feats, and
quotidien selections like spell selection, weapon selection, Wildshape form selection etc.
This is before localized campaign factors....things like a DM giving the role playing hook that people with the a Healer feat trained with the Maesters of Oldtown, for example, even come into play.
The system, largely, produces characters that are unique, allow the player to make
meaningful choices from a manageable list of options and still retain parity with other PCs, and is, overall relatively, quick in terms of time invested.
I like that there are many different avenues to approach a design goal in 5e.
Knights of Solamnia could be represented as an organization like the Order of the Gauntlet in the Forgotten Realms, or like Guilds in Ravinica, or even as a subclass available to Fighters, Paladins, and Rangers.
One does not need to build bespoke 'classes' like in prior editions.