It’s easier than that, it’s not feeding on the creatures protein and fat it’s predating on the creatures soul, or pain.
A creature of this size wouldn’t get there or stay there on victims stumbling into it. Especially in the deep desert, it’s victims are likely few and far between. When it gets a conscious species, it tortures it for 1,000 years until the things’ spirit and consciousness merge with the hive mind. They are clearly putting energy into maintaining the life of the victim.
I do a different kind of imagination work in my head for mysteries like this. The way you think seems very mundane and boring.







You prefer your fantasy that happens in other worlds to be more grounded? It’s amazing how boring this world view is.
I will allow authors to take me on a ride and I will fill in gaps where needed. Frankly I have no reason to believe a Sarlacc in this world does any of that, how did the people in the star wars universe figure that out? Maybe it reads more like a boogeyman legend about a creature the Hutt’s use to execute people. I might add that our only in world evidence is boba fett getting out of one, not super scary. I’m just adding a bit of my own spice to the world because it’s been left open to me to do so. That’s fun!
Imagination and thinking are the same thing, you have to think to imagine What an unusually dull world you inhabit!