Let us clarify a few details and see if we can rule a few things out here shall we.
- Its a ps5, so machine too slow?

I have a main base and several outposts. I do not evoke purges at my main base. Instead I do it at a designated outpost.
- The outpost is, 5x6 foundations, two wall pieces high and a single story. In the way of followers, there are currently 5 archers there. So base too big?

Let us now move to current list of treasures at the outpost designated for purges.
- ancient lemurian statue x5, derketo cat idol x2, bountiful treasure chest x2, golden Argossean brazier x2, embellished amphora x2,gilded urn x2, finely decorated plate x1, jade warhorn x1. Not even enough to get to level 10, so ‘gigantic treasure collection’?

I am also an Singleplayer, so server traffic is not an issue for me. It further makes no difference if I play online or offline.
Happy to give that a try, it would not be as loborious.