Some points and responses:
(1) There is a degree to which the idea of magic item shops is the fault of the (non-Core) rules (like the MIC), but there is nothing in the Core rules, IMHO, that implies magic item shops. Moreover, I do believe that some of the tag-on rules are, in effect, "booster packs" for the game. In 2e, the Complete series was also booster-packy, so this isn't new with 3e.
(2) Being able to customize order an item from an artisan is not, in any way shape or form, the image that comes to my mind when one says "magic shop". I fully agree that individuals will exist that custom craft. Many mundane items for that matter, such as plate mail and ships, should only come into existance as the result of custom crafting -- no one in their right mind invests that kind of time and effort in the hopes that a buyer might come along.
(Mass production and an industrial economy changes this quite a bit; but even that is a relatively recent phenomenon for big-ticket items, and probably relates to the success of the automobile IRL.)
(3) I do believe that a certain amount of "fuzziness" is desirable in a RPG ruleset, yes. That said,
(4) The "delightful potion-mixing rules" were brought up as a counter to Storm Raven's ascertation that magic in D&D was always "a predictable technology". That is simply untrue, as an examination of the rules in question easily shows. Those delightful rules are, in essence, the polar opposite of predictable technology. From
wands of wonder to
bags of beans, 1e was chock-full of unpredictable items that otherwise had no model in the rules.
(5) Darkseraphim's point is accurate (not that he's the first to say it), whether the items are all easily located in a big box store or in a city....and that is the flaw that Wal-Magic model implies.....if you can just get the same items in town, and it is easier to do so in town, why go into a dungeon at all? Why not treat towns like dungeons? For that matter, if there is a thriving magic market, why wouldn't you just craft items and not adventure at all? You can claim that the term "Wal-Magic" somehow creates the problem as a strawman, but the problem is there no matter what you call it.
(6) Not everything can be special. It's perfectly OK that your boat means more to you than your magic shortbow.
(7) If you are trying to create a post-industrial feel, magic shops fit right in. Victorian Era? Magic shops fit right in. Spelljammer? Magic shops (ala the Arcane) fit right in. Other settings, not so much so.
(8) It is against the directly stated intent of the game in both 1e and 2e that magic shops exist. In that sense, the idea violates the previously existing "spirit of the game" (although it should be noted that in 2e, Spelljammer specifically and intentionally violated that spirit, and the Arcane appeared in the MC, which made that violation "Core"....Which is a really weird sort of shitzophrenic take on magic shops at best).
(9) On anothe thread, I suggested that if "because the players want it" is a valid reason to include something in a game, then why not tactical nukes? The response was that high-level casters are effectively tactical nukes. Extrapolating from that, if high-level magic is like tactical nukes, shouldn't the availability of that magic be something like the availability of tactical nukes IRL?
(10) In any event, you are certainly entitled to play the game however you like.
