The problem is, what is prior art? It's highly subjective and as such, the law is complicated.
It's anything in the art that was published or available to the public prior to the filing date of the application. There's nothing subjective at all about it. The Model T is prior art for the Tesla Roadster. UNIVAC is prior art for the Macbook Pro.
What you seem to be referring to is anticipatory prior art - that is, art that includes every element of a claimed invention. But even that is not subjective - either it describes the claimed features or it doesn't.
What you really want to be referring to is "what is obvious?" And that's a little more subjective, but not as highly subjective as you think - under the current law, if no one reference describes everything in the claimed invention, nothing anticipates it or it is "new", but if a combination of references teach everything in it, then it's obvious. So, if the invention claims "A+B+C" and one piece of art teaches A+B and the the other teaches C, then A+B+C is obvious. That's not very subjective at all.
There is no reforming the current system. We need an entirely new system. As is, an inventor has basically no change to win. If he invents something, lawyers find a way to subtly change it to produce it without permission.
In other words, lawyers (or other engineers) find a way to invent around it. The public ends up with two ways to accomplish the same thing. Innovation is increased. Hooray!
Likewise, if they have something patented they again get lawyers to find a way to change it and extend that patent into perpetuity.
In other words, lawyers (or the inventor) find a way to invent around it, or come up with an improvement. The public ends up with two ways to accomplish the same thing, or a better way to accomplish the thing. Innovation is increased. Hooray!
Patents should be rare. Almost everything should be covered by short term copyright and trade secrets. Patents should only cover truly new and innovative tech. Smartphones are battery powered computers... there shouldn't be anything in them that's patentable.
What about the better batteries? What about wireless charging, fast charging, new battery management techniques that extend battery life, etc.? What about new transmission and data compression techniques that make that new smart phone able to communicate ten times faster, over ten times the distance, as the old model?
A new form of Fusion reactor? Ok... that's patent. I'd even propose that someone applying for a patent should have to get a court to approve the patent before it being granted.
But let's say we go with your suggestion... No patents since they'd be way too expensive if you have to go through an entire trial just to get exclusivity before you even start making your product. Instead, "short term copyright and trade secrets".
Well, copyright doesn't apply to that smart phone, because when your competitor makes one, they're making a new one, not copying yours. In fact, copyright only really works when you're copying the exact thing - rip a DVD of Harry Potter and you've committed copyright infringement. Film the Mockbuster production Larry Kotter, and you haven't. Dream Heights isn't an infringement of Tiny Tower. GIMP isn't an infringement of Photoshop. A Nissan Leaf isn't an infringement of a Toyota Prius. As a result, copyright doesn't work when people care about the implementation, but not the exact thing. It's fine for movies and music and books, but not for software or hardware.
So, we turn to trade secrets. Great, now you have to sign a contract with every piece of software or hardware you buy. And those contracts can last a lot longer than the limited term of a patent - they can be lifetime contracts. Don't like it, don't buy the software or hardware - but without patents, every manufacturer is going to insist on non-disclosure agreements and non-reverse engineering agreements, so no smart phone for you.
Patents exist to destroy trade secrets - in exchange for public disclosure, we give a limited monopoly to the inventor. The alternative is going back to trade secrets, guilds, aristocratic patronage, and companies that hire mercenary guards to keep anyone from ever discovering what goes on behind closed doors. And that's bad for innovation.