When the hole for my foundation was dug 43 years ago I knew little about excavation. Most cellars here were dug with dozers at the time. My soil is boulders, they are typically potato shaped, some as big as a HUMVEE.
It was dug by a family I've since become very close to. The boss sent his nephew to dig it. He unloaded an International 150 track loader. 150 model comes from 1.5 cubic yard Drott 4 in 1 bucket. I'll guess the machine weighs 20,000 LBS.
It took days to get 11' deep in all the impacted boulders. After that it was somewhat quicker. Drag backward to knock down a big (typically 2 cubic yard) rock, get it into the bucket. Only a few spots was he able to scoop a bucket full of gravel. The little bit of gravel he found was needed to give the machine something under the tracks.
I never see a new track loader. Charlie Abbott loved them, probably owned 20 total IH 175 model. I feel track loaders have been replaced by faster working machines.
They seem slow to me. Before the big excavators became common, loading in a gravel pit was mostly done with cable shovels, a VERY efficient way to load. A good operator can load keeping up with several tandem haul trucks.