I would agree that magic items in older editions (pre-3e) tends to be wackier, more flavourful and more "magical" than modern ones. I think there are several interconnected reasons for this:
1. Rarity. In older editions, magic items were much rarer. Whether you get any magic items were purely up to the DM. But from 3e on, the game expects a character of a certain level to have a certain amount of items in order to face the challenges expected at those levels, causing a proliferation of magic items in modern games.
2. Balance. Modern games are more focused on balance and thus DMs have to have an idea of how powerful a magic item is, whether by assigning a level or a GP cost value to the item. In order to do this, the magic item has to be analyze-able. You have to be able to assign values to the effects of said item. Once you can analyze and do math with the effects of an item or magic in general, mysterious magic quickly becomes applied science.
3. Rules vs. DM ruling. In modern games, RAW is king. The DM has to make his rulings consistent with the rules of the game, rather than make completely arbitrary rulings. So, in order to maintain game balance, magic items and effects have to be codified and presented in simple, concrete terms describing exactly what they do, to allow the DM to make quick, accurate judgements. The easiest way to do this is to standardize the magic items and their effects. And also because of the importance of RAW, the magic items have to be created to fit into the rules framework. If you have a magic item A that can cast three wish spells and if a wish spell can create a magic item of item A's power level, you get an abusable loophole in RAW. This is a much greater problem in modern gaming due to the RAW>DM paradigm.
4. Secondary Magic Market. In 2nd ed and older editions, magic was pretty much untradeable. I've never encountered the mage-mart idea until 3rd ed. But the existence of magic item trading in modern game means that a magic item has to be useful to the player or it gets traded for more useful items. Since magic items can now be analyzed and compared, it's easy for players to see which items are more useful or powerful. Wacky, oddball items are only used to overcome challenges in funny, memorable ways because the players didn't already traded it for something that would allow them to overcome the same challenge in a conventional manner. Would you rather have item A which is cool in theory but unreliable and might only be useful a few times sometime in the future, or trade it for item B which is more mundane in comparison but is reliable and always useful? Most players would choose item B. A lot of players want simple, reliable items that they know would add a certain amount of power to their character rather than complicated items with unreliable abilities that rarely gets used.
Additionally, many creatures required +X weapons to even hit, so naturally many campaigns had to include magic weapons.
