5e does low-magic parties fine
Low-magic in the sense of low-magic-items, certainly, and even low-magic in the sense of no-full-caster PCs (you loose half the PC options, but you still have Paladins to offer some support, and a range of other contributions from the remaining half-casters, and the technically magical Monk).
but it'd be nice to have more official options that don't cast spells or do magic-y things. Not exactly necessary, and I wouldn't say that 4e did it better, but it'd be useful.
It's not exactly necessary for an FRPG to handle a complete lack of magic, certainly - except that 5e is trying to broaden the range of playstyles it supports to at least encompass those past editions did, and low-/no-magic is one of 'em.
The 5e PH offers 0 non-magical classes, and 5 non-magical sub-classes out of 38. All 5 of those sub-classes are DPR-focused ('Strikers'), they are virtually choiceless compared to the unprecedented flexibility of the neo-Vancian caster classes. The 4e PH offered 4 non-magical classes out of 8, and 8 non-magical builds out of 18, covering 3 out of 4 roles (the most dispensable role, Controller, being the one left out). All 8 classes were robustly balanced and only the Wizard had a little more choice/flexibility than the others. It's hard to characterize that as anything but 'better.' Indeed, even if you would say 'did it better,' you'd be guilty of a profound understatement.
5e however, as the current edition, and one that emphasizes modularity and the potential to support multiple play styles, still has every chance to make up that gap. A couple of really engaging, flexible new classes with all/mostly non-casting sub-classes, able to handle the rest of the informal/implied roles needed in a 5e party could do it.
Mayhaps one could create a class that uses the spell slot paradigm, but their spells known are actually various weapon techniques. I see no part of this idea that would be remotely controversial.
Very funny. Actually, Battlemaster CS dice are pretty close to Warlock spell slots. If Warlocks could only learn 6 spells, out of list of only 17, and all of them being 1st level, that is.