Getting a call from any IIM is never a waste of time. Once you're invited, don't worry about whether you'll get in or not, just do your best. Focus on preparing for the interview. If you're accepted, look into the fees and the job opportunities (IIM Jammu Highest & Average Package for batch 2023 was recorded at INR 64 LPA and INR 16.50 LPA respectively). If you're happy with what you find, it's a good chance. If not, it's not worth your time.
However, the decision is up to you. IIM Jammu is one of the new IIM but if you do well there, you could land a High-paying Job, possibly over 15-20 LPA, and save a year. On the other hand, if you think you can do even better in the CAT exam next year, aim for the older IIMs.
It depends on you whether you can afford to take one gap year and give CAT again next year or not. If you can afford to take a gap year, then giving cat and preparing diligently is definitely a better option because you might get into old IIMs ie. BLACKI and if not, then IIM Jammu is a good option.
You’ll get that IIM tag which will benefit you in the long term and in terms of placements, a total of 257 offers were made to the students. The highest CTC stood at INR 64 LPA, while the average and median CTC stood at INR 16.50 LPA and 15.25 LPA respectively. The average package increased by 19.7% over last year.
So, it depends on you what are your career aspirations and how you want to proceed further.