I'm in graduate school now, and I took some CS courses in undergrad ~20 years ago, and fundamentals haven't changed as much as the superficial garbage that is all the rage in industry. There are new approaches and capabilities, especially around deep learning (largely because we've replaced the push toward higher clock speeds with a push for parallelism, and almost everything is close enough to a parallel problem that a neural net can do the job), but the fundamental ideas don't change that much because real computer science (as opposed to industry wankery which pays $500,000+ but rots your brain) only accepts ideas when there's at least some evidence they actually work.
So, if you studied computer science in 1990 and kept the knowledge up, you'd still know a fair amount of what's relevant today. The problem is that what's employable isn't actually computer science, but trendy industry nonsense... the real CS is just in place to be an IQ test, a first-line hiring barrier.
So, if you studied computer science in 1990 and kept the knowledge up, you'd still know a fair amount of what's relevant today. The problem is that what's employable isn't actually computer science, but trendy industry nonsense... the real CS is just in place to be an IQ test, a first-line hiring barrier.