Interesting. When i do that, I find that questions that were unanswered then have been answered. I find that the basic principles are the same. I find that the overall picture is the same. I find some details different, but I expect that.
What do *you* find?
Oh, I also find that debates that were hot previously have been resolved because of new evidence. I find that things people speculated about are now known one way or another.
So, for example, when I look at physics texts from 1988, I find that they have almost identical information at the lower levels. At the upper levels, things that were uncertain then are now resolved. For example, in 1988, there was a HUGE question concerning solar neutrinos and why we see so few of them. That issue has now been resolved (neutrinos have a small mass which allows them to convert between the three types). If I look at astronomy, in 1988 we knew of no planets around sun-like stars, so many aspects of planet formation were unknown and speculative. Now, we know of thousands of other planets and those questions have been resolved.
If I look at evolution, the last tail of the debate about Punctuated Equilibrium and its role was still going on. That has mostly been resolved. There were questions about the evolution of birds that have now been resolved. We know more details about the evolution of great apes and humans than we did then: many of the debates then have been resolved.
Now, if you asked today whether there are planets around another star, you might well be laughed at when that would have been a live question in 1988. That's what happens when answers are found. If you asked in 1988 whether relatives T Rex had feathers, that might also have been laughed at: no evidence was known for such. Now it is known through fossil evidence.
Science *always* has open questions. For those questions, there is always a lot of speculation. But the parts of science that are *known* grow and those speculations are determined to be either correct or not after new evidence is found.
/E: But I'd also point out that in 1988, Fermat's Last Theorem was still an open problem in math. The Poincare conjecture was still not resolved. So even mathematics has changed in the last 30 years. NOT by throwing out the old ideas, but by finding new information and refining them into the new ideas.