Creativity is finite.
It's an uncomfortable statement, but it's true. It's why you'll see comedians
recycle old jokes. Why your favorite band's new stuff isn't as good as the old stuff. And why doing a remake of a series/movie is easier than making something new. People get writer's block, they run out of ideas, and they face
burnout.
Product
overload has pushed everyone to their limits. Consumers can't keep up with all the new releases. Game stores are having trouble with purchasing the right stock that will sell, often leading them to buy copious amounts of a product that won't sell, or too little of a product that's in demand. And card designers have run out of ideas. It's getting harder and harder to make something unique and special that isn't just a rehash of older cards. And to meet deadlines, sometimes they must.
Credit where it's due, Universes Beyond helps with this. The characters, items, and settings give a prompt for designers to work off of. Think of a lightsaber; a sword that can cut through anything. So as a simple design, it's an equipment artifact that destroys a non-lightsaber artifact when the equipped creature attacks. Done. Designed. All that's left is to work out the mana and equip costs.
But even still, there's a lot of product coming out. So of course card designers will default onto something familiar. It's easier to
balance, and you don't have to think as much when designing the cards. By rehashing old mechanics, designers can pump out the cards quickly and move on to the next thing. Just as Hasbro intended.