Last Rites on PS5.

Hi! I had this same issue in my game as well. I play on PC, so I'm not sure if this will help you, but hopefully it will;; 

I'm not sure if what happened with me was part of the issue (or what the issue is entirely) but I had the hidden treasure quest and Last RItes active at the same time.

My solution was to reload to a save before I even activated/accepted the Last Rites quest. I then did the other surrounding quests in Dock Town, cleared those out before interacting with the note about the Venatori to activate Last Rites. 
When I did get the quest active (with no others active at the same time), it seemed to have loaded the crystal walls/barriers around the ritual site correctly (they did not appear for me at all the first time, just the floating red crystals) and I was able to destroy the crystals to access the note beside the body at the ritual site and progress with the quest. 
I suppose you could just reload to before accepting the quest and doing that solely (and skipping what I did and clearing other quests so long as those are not active as well?) if you're willing to do a reload, and if you haven't progressed super far yet.