One would and should expect better than that, and unexpected declines happen, often. The Sox saw almost all their returning vets decline, all at once, and some were in or approaching their prime years.
Stanton turns 34, later this year. One would expect a dropping OPS, and that's what we see, His OPS dropped more, last year than it has this year:
.887 2020
.870 2021 (-17)
.759 2022 (-111)
.708 2023 (-51)
DJ turns 35 in a couple weeks. He dropped 300 points from 2020 to 2021, and he's just 32 below his '21 numbers, now- 2 years later. One might have expected more of a drop.
Donaldson started his decline before going to NY. He turns 38 in December.
.950 '16-'17
.875 '18-'19
.829 '20-'21
.686 '22-'23
He's actually improved on his '22 .682 OPS by hitting .724, so far. One could argue he's doing better than expected.
Rizzo turns 34 in August. His decline started long ago, but he was still hitting well.
,914 '16-'17
.883 '18-'19
.775 '20-'21
His .817 in '22 could be viewed as a blip.
.768 in 2023 is maybe higher than one might expect from the '20-'21 numbers and the age curve factors.
I'm thinking much of this should have been expected, but people tend to look at teams and players as they used to be, and forget about injury proneness and age decline projections.