I agree that your academic qualifications appear to be competitive anywhere. Some colleges are low probability for anyone, but you will be in the mix. I would not worry about your ECs–just be active and enthusiastic.
I also agree you should NOT think you cannot write essays that will help you get admitted to very selective colleges, but you have to understand what that means.
Taking a step back, the most selective US colleges are mostly holistic review, and among other things that means being sufficiently academically qualified is just part of what they care about. They also want to have a clear vision of you being active in their community in other ways, hence asking about activities, and finally that you will be the sort of person who really thrives in their community, both benefiting from it and contributing back to it.
But there are many ways to excite them about what you would be like in their community. In some circles you would get the impression they have a certain formula they want all their admits to follow, and an application is a test to show you scored a 100% according to the formula. That is usually the exact opposite of what they think, they actually want to blend together different people who will all benefit from being in a diverse community. Different interests, different activities, different backgrounds, different goals, and so on. But the common denominator is understanding that is their underlying goal and showing you would thrive in that community in your own specific ways.
OK, so your essays are your opportunity to show you understand what they are trying to do, are excited about what that means for you, and to give them a clear vision about how you would thrive at their college, both receiving and giving.
And you can do that!
But here is the REALLY big trick. You can do that best if you actually mean it! Like, you didn’t just apply to any college because it was ranked highly in some magazine, or is in a certain football conference, or so on. Instead, you spent the time to carefully look at what different colleges are like, to imagine what it would mean for you to be in those communities, and then you ultimately chose the ones where you were particularly excited about what that specific college could mean for you, both academically but also non-academically.
OK, so since you are just a junior, you have plenty of time to do this right. Why Illinois? Why Michigan? Why Northwestern? What appeals to you about those schools specifically? Have you considered other types of schools? Maybe visited some different schools just to see what they are like? Start broad and open-minded, and only gradually narrow down as you really start refining your preferences.
As a final note, I think a lot of people do this in the exact wrong order. Once you really know what you like, reaches are easy. The fun ones are the likelies and the targets. There are so many colleges out there that would love a kid with your numbers. They have all sorts of different departments and programs, different formats and settings, many offer merit scholarships to try to woo kids like you . . . . Exploring these schools and ultimately deciding which excite you the most is the fun part. Then adding in a few reaches as well along the same lines is the easy part, to the point it is actually kinda boring because it becomes so obvious.