Is it worth joining IIM Calcutta for a person with average/below average profile?

First let's sink in the fact that anyone who gets a call from IIM Calcutta is anything but average or below average. The fact that you got selected is enough to claim that you are not below average.

But if you still consider your profile inferior to others then you need to put in extra efforts within the institution. Honestly even the above average students have to put tremendous effort inside any IIM. Look at the bright side. You, being a below average student, just need to put in more effort than an average student to get at a level equivalent to that of an above average candidate.

So yes, it is worth joining IIM Calcutta with whatever profile you have.