You're not limited to only graphics, code and music assets. You've also got character designs, characters, plot, background, potentially an entire world. Those aren't going to date as graphics and sound assets are. Moreover, they are likely to attract the old audience.
I never said anything about abandoning IP protection wholesale, just moderating it to make it more realistic.
You're right though, Shakespeare's decendents should be kicking and screaming right now. Really though, JRR Tolkien's kids are the ones that should be mad about most videogames. Most popular plots for movies, books, and yes, even games are heavily based on existing older ideas.
Let's indulge you though, what happens when IP becomes free?
Disney has remade loads of old stories into movies for example. Those movies have added to our culture. The fact that stories like Snow White are free to be exploited have meant that a great movie was made. Ever seen another version of Snow White? The Disney version was better, right? Just the fact that others can exploit an idea does not mean that it's completely free. There's still work to be done in any production, and you'll still profit or lose based on what you put into it.
If Disney's Snow White ever goes out of Copyright, could you copy it wholesale and sell it? Yes, of course, but so could everyone else, meaning there'd be NOTHING to be gained from doing that kind of thing. That's why all those old literature books now go for $5 at your bookshop. Isn't it great how everyone in Australia can read The Great Gatsby on the cheap?
What would be so bad about a say 10 year copyright on video game software? If the originator of the property sees that there's profit in doing a remake, it's up to them to do it. If not, someone else can profit on it. They'll succeed based directly on how well they manage to imitate the originators to satisfy the fanbase. The originator still made their money from the original, right?
As for derivatives, loads of people have made loads of different versions and even derivatives of Dickens' A Christmas Carol for example. Has this diminished the value of his work or added to it? Have subsequent people profited from it?
My issue is that this current environment of IP means that no future generations will get their own Christmas Carol to build on. Even worse, they might not be able to enhance or improve medicines, industrial designs, etc. because that would violate someone's 50 year old IP. To get why this is bad, you have to look past your own wallet and look at what's good for society as a whole.
If you're worried about someone someday stealing your stuff and making their own derivatives of it, don't. Look up "fanfic" to see why. If your work is quality, it'll be remembered, and benefit generations to come.