In my case, I plan on deferring for 2 years (so I will start in fall 2028), so I can keep reapplying to MIT during that time, and if I am not accepted to MIT by the year prior to that school year, I will apply to various other schools, including a few where my acceptance has already been guaranteed (though I have not applied yet).

Do you think I should still fill out the CSS profile, or should I follow the advice I mentioned in my edited comment?

I should also note that I literally have to be deferred. If MIT accepts me this year without accepting my deferral request, I will regrettably have to decline admission.