That'd be disagreement, then, since I wouldn't want to see "minor" playstyles (how'd that even be measured) fall through the cracks, either.
I don't
want to either, but the world is imperfect. There are a finite number of pages in published books and the writers are paid for their time.
If I tweet Mike Mearls with a feature request on Twitter, I don't really expect him to stop and design that just for me an my table. It has to have broader appeal. Of course, neither do I expect them to only design content that they expect will appeal to 90% of tables.
They design for someplace in the middle. A wide audience. Things that many tables want.
No, not IMHO. It might be an element of a playstyle, but it seems to me the option is there for 5e DMs who want a style of campaign that would need such things.
For simple things, sure. For something that takes a couple hours to write and a couple more hours for someone else to edit and give feedback on, sure.
Especially if it's something not already supported in the game.
The problem here is that the rules for making magic items & buying/selling magic items are already in the game. There
are rules. The complaint is they're not robust and detailed enough.
For someone running a horror campaign, the fear, horror, and sanity rules are also a little weak. And the lingering wounds rules aren't great for someone who wants a gritty game without regular maiming. But adding new variants of those rules will always be a lower priority than making brand new rules for unsupported gameplay.
And making those new rules is largely simple and not complicated. A magic item economy? Crazy hard.
As an example, 2nd Edition had a system for making classes in the
Dungeon Master's Guide. Compared to that, the class design rules in the 5e DMG are a joke. (To say nothing about the options in
Skills & Powers.) But making a large robust system (likely point buy) for designing classes would not be the most efficient use of time. It'd be impossible to balance and require laboriously going through every option in the books, assigning arbitrary value in a near vacuum. So you'd be spending a lot of time to make rules that only kinda work while presenting the deception of a balanced subsystem creating a trap for Dungeon Masters.
Magic items are the same. There's no way to assign an exact price to a magic item. But without fixed prices, a firmer crafting system wouldn't work. Similarly, designing magic items themselves is more an art than something you can do with a formula.
It'd be just as effective (and balanced) to go through the DMG and assigning a random number to each magic item.
Plus, with 5th Edition, magic items inherently unbalance the game. They're a power increase for the players, and putting their creation and selection in the hands of the players rather than the DM is outright broken. It's trading something that doesn't confer a mechanical benefit in the game (gold) for a bonus. It's a little like allowing players to increase their ability score or gain powers by training using downtime days.
("I spent two months working out, so my Strength goes up by 2.")
I don't think that's fair: different game elements, depending on what they're trying to accomplish could require very different amounts of support, however you're measuring 'size.' More robust rules for creating magic items would be rules for breaking the balance of their system.
Making the Artificer a full class, for instance, is a much heavier solution than making it a Wizard tradition, but they're goin' there (and, really, for a narrow concept that's appeared in only two editions, and only off in the supplemental periphery of those). A hopeful sign, in a way.
I'd hesitate to call the "artificer" a playstyle. It's a rules expansion, but very different than the optional rules and subsystems needed for customisation. And while it takes a lot of work, that work can actually result in a balanced product.