I didn't say, nor mean to imply, that all magic items in AD&D were ho-hum. A flametongue wasn't, for example, and clearly is a more interesting item than 4e's flaming weapon.That is a key point right there.
It was easy for magic items to become very ho-hum in prior editions of D&D. But in the end it was 100% up to how the DM ran the game.
Yes, the DEFAULT was ho-hum.
The "math works" of 4E changes things.
There are various factors that explain this - for example, besides its inherent variability vs various sorts of opponents (+3 vs trolls, +4 vs undead, and I think +2 vs birds), a flametongue is interesting because it gives the PC a schtick that s/he didn't have before. Whereas 4e PCs get their schticks from other build elements, and items are ancilliary to that.
I personally don't think the "maths" is as big a difference as you suggest. AD&D had its maths too. If PCs don't have +1 weapons, then a good chunk of the Monster Manual isn't going to see as much use as it otherwise might. (Although the maths progression is not as steep. From memory, only Fenris Wolf requires a +4 or better weapon, and I think the gargantua from Oriental Adventures may require +5s. And demi-liches, of course.)
But often there isn't. For example if, as per the advice to GM's in both AD&D and Basic, the NPC/orc chieftain/whatever is using the sword+1/wand of magic missiles/whatever, then when the PCs win the fight they may not have much trouble acquiring the loot. (In AD&D, the magic blades will even be evident by the light they shed.)Those tables guarantee placement. They do not guarantee acquisition. There can be a world of difference between the two.
I've got no objection to the claim that 4e magic items play very differently from AD&D items in all sorts of ways.
But I've played a lot of Basic D&D and AD&D. And in my experience, finding a +1 sword was not, in general, a semi-major event. The first one for a campaign may have given a bit of a thrill, but then that's also true in 4e - my players were excited to get their +1 enhancement bonuses.
Others may have had players who were more easily thrilled in classic D&D, and/or more jaded in AD&D. But I know what my experiences were, and continue to be.