There's no point in learning it. You can learn all the enzymes in the periplasm of a gram negative bacteria and design theoretical antibiotics, but that still doesn't mean dick for the patient in front of you. Likewise, knowing the 4 different types of estrogen receptors can make for an indepth Grand Rounds discussion but in the end, nothing changes for the patients. The folks who care about this **** are 10-50 years away from making viable drug targets and after that, it takes like a week to get up to speed on the physiology of those pathways for the average clinician.
In the end, we are just looking for ways to justify all the crap we learned for Step 1 and for the most part, none of it really matters. Does knowing that GHRH acts via cAMP do anything for the patient suffering from acromegaly? Or that GH is a non-receptor tyrosine kinase pathway while all the growth factors are receptor tyrosine kinases? Unless you are in pharma research, no, it doesn't really matter.