You are very much not alone, and I don't think we're all getting dumber -- I kept using opus 4.5 all through the nonsense that was 4.7, 4.8, and 5, and kept having a good time :)
I think we just need to decouple "doing better on benchmarks" and "actually more useful to me", since they've clearly diverged
doesn't that just mean that either a) you're using the wrong benchmark to judge or b) the benchmark that YOU need doesn't exist.
That's not the point, the point is that the company making the product is optimizing for the benchmark and/or the apparently idiosyncratic preferences of their own team, and not for the user experience of their paying customers.