Am I the only one sick of hearing we don't need X subclass just take Y Background or BM/Champ. If these people were listened to we would never see another damn subclass again. Subclasses allow for greater mechanical representation for a niche or flavour and this is what some of us want to see and consider just adding a background or flavourless mush that are BM/Champ to be boring or mechanically not far enough.
I understand your point. Thats why I normally never post such suggestions unless I think its productive. Cause everyone likes different stuff.
Having said that, I rather enjoy the way 5E lets you put together bits and pieces and form a "new" concepts. I do like unique mechanics when they bring something to the character, but as a whole, most of our concepts can be built, for example;
Elven Swordmasters: Low level, dueling fighting style, Feat: Martial Adept (Standard Swordmaster Maneuvers: Evasive Footwork, Precision Attack, Riposte.) Higher level, more commitment = levels in Battle Master
Nightblades: Rogue/Shadow Monk
Witches: Warlock base, access to druid spells, normally Pact of the Tome.
But, I agree there are mechanical voids, artificing, imbuing arrows or weapons, psionics, spellfire type mechanic, etc. are some of mine.