mearls said:1e and 2e had a sort of, "Close your eyes and pretend it isn't a problem" approach to magic items.
Are you sure? Maybe 1E/2E just thought it wasn't the *game systems* problem. I don't understand how DnD could, in part, be a "resource management" game and yet there's no variability (or over-regulated, illusionary "variability" based on the reputation gained from prior editions) in the resources character's possess.
Even if you drag out the rusting effects of the rust monster, over the long run players are still facing an X% chance of losing their magic sword to the monster.
So a player is still going to lose their sword to a rust monster. Or are they? Drag it out long enough and perhaps there winds up being a close to 0% chance that any rust monsters attack will actually be able to jump through all the hurdles necessary to destroy a sword. At this point you're really just coasting on a *reputation* of the rust monster to destroy items (reputation thanks to 1E). At some point, people will catch on to the idea that the actual mechanics make it not that much of a threat.
Same thing as character death. A DM can get by for so long fudging to keep characters alive. Sooner or later players will recognize that they're not going to die, and the "thrill" of risk taking will be gone. Now the game system seems to want to do the fudging for them.
I don't think that designers should think that removing the possibility for short-term failures in the game is going to make things more fun in the long term. That's what makes a Monty Haul game fun, probably, the first time you play, but less so each additional time.