But Auto HDR isn't nearly as good as native HDR support, as this game demonstrates
Imagine actually believing such heresy
I agree, they definitely could've done much more. But, realistically speaking, they're already working on the next GTA, so it likely wasn't a priority for them.
On the other hand, when I look at the upgrades Sony has been charging $10 for on PS5 (Uncharted LoT Collection, Ghost of Tsushima), this compares favorably. The only worthwhile upgrade from them was for Spider-man Remastered, but that was for $20 (and bundled with Miles Morales).
Of course, a free upgrade would've been ideal, but only a few games have offered that thus far, and even fewer ones have been worthwhile (e.g. Metro Exodus and Ghostrunner).