Shackleton may not have made the pole (a somewhat everyday accomplishment now). What he -did- do though will, I suggest never be repeated.
He (and 5 of his crew) crossed the southern ocean, from Elephant Island to South Georgia in an open life boat. A distance of 1500km in 16 days. Nothing comes close to this. Then, on arrival, he crosses South Georgia on foot with woeful equipment. This leg alone is a rare feat even today - usually done by well equipped special forces of planned expeditions.
His ocean crossing though stands alone. Nobody is lining up to repeat it - its almost certainly suicide.
The book of the expedition is public domain on kindle, and we'll worth a read. For the short version see https://nzaht.org/encourage/inspiring-explorers/crossing-sou...