I feel like this might overestimate the decline if there is also a shift in what sci-fi titles tend to look like, which feels plausible to me given that titles follow trends. Anecdotes aren’t super informative granted, but anecdotally, virtually none of the more recent sci-fi media that ive seen contains those keywords in the title (and most of the exceptions are newer additions to older franchises), and most titles I can think of with them are quite old. This need not mean sci-fi has given up on starships or whatever, but it might imply that, while we are still a long way off from building one, the concept of such things is no longer new, and so merely implying that a work features them is no longer enough to make it stand out.