See if you are determined about your career ahead then I would recommend you to obviously take a drop because as IIT is the place you want to study and if its in your passion then you should prepare very well in this drop year. It may seem that one year will pass by but always remember if you get into your dream college all this hard work will pay its value. Now let me say a fact, IIT's or a degree don't give you a job. Its good that you want to be in IIT but you should be aware that you like CSE as well and you are enthusiastic about the subject because if you get selected then you have to deal with CSE subjects. So made it clear that you are interested for IIT and the subject or you are just participating in the race of fame. If the answer is that you are interested in CSE and to get a better scope and structure you want to be at IIT then you should take a drop year and let me assure this will drive you very good towards the success.

To know more about JEE ADVANCED preparation strategy you may visit the link below:

https://engineering.careers360.com/articles/jee-advanced-2021

I hope this answer helps. All the very best for your future endeavors!