You generate huge stacks of Holy/Unholy weapons. Make Create Water devices etc etc etc. Come on you don't even have to think that hard to screw up a world with those unintentionally.
I'm trying to focus on the ways you can unintentionally, or even with the world's best interest, screw up the world badly.
You can look at our own world. We could easily feed everybody out there and give them medicine with our current technology. But we don't, because it wouldn't be profitable.
We know how to make artificial diamonds, but we still send people down to the mines and get "natural" diamonds that are much more expensive, and guess what, people still buy them for the extra price!
Meanwhile trillions of dollars are spent developing new and more sophisticated ways of killing ourselves, and the only reason we didn't glass our own planet is, ironically again, it wouldn't be profitable (a glassed region is a region where you can't set up shops).
To add to the crazyness, all of this is be done for pieces of paper and virtual numbers. We have atomic bombs and bombers and whatnot, yet we don't trade them in some kind of rare substance that is impossible to duplicate, but in mass-produced pieces of paper and floating numbers in computers.
So no, simple mass production of magic items won't be enough to colapse the world just like mass production of technology didn't colapse ours.
Now what colapses the world, is if a serial murderer can grow nukes out of his pockets if the police doesn't catch him soon enough (aka murdering psycho geting to enough level to start casting the big spells by himself).
Like nuclear power, magic does nothing on its own, but must be wielded.
Those are both blatant lies and you should feel ashamed of yourself for saying those.
The sun? It works on nuclear fusion. The Earth? Natural fission of elements heats up the interior and slows down the cooling. Whitout either, our planet would be a frozen ball and we wouldn't be having this discussion.
D&D magic? It animates by itself. Not all monsters are the result of bored wizards, far from it. Plenty of monsters are basically magic gone wild and developing a will of its own.