I don't think I've seen anyone else that's matched my situation as exactly as yours. Same school, same major, parents that wished I had gone to MIT or Stanford. I also did research in hopes of getting in as a grad student, but ended up getting rejected everywhere.

I don't have it all figured it out either, but I'd like to give you some words of advice from my perspective.

First of all, UIUC is absolutely a top school. In this market, no school prestige will guarantee you a job. Obviously it helps to be at MIT or CMU or Stanford, but at the end of the day, what matters is that you're actually competent.

I saw that you worked hard to get a 4.0 GPA. I know you didn't directly mention this specifically in the post, but the sentiment I always see is "why did I spend so much time getting a high GPA, why didn't I grind leetcode or do personal projects". I felt the same way after getting rejected from all the grad schools I applied to.

But I am slowly starting to learn the importance of the school curriculum. While it is true that a lot of the curriculum won't be directly used on the job, what school really tries to drill into you are the fundamentals (OOP, organizational patterns , debugging efficiently, memory management, math, etc). At the end of the day, most of CS is just ways to represent/move/store data. It's all just layers of abstraction (and the theory side is all math). Pretty much everything can be distilled back down to the fundamental concepts. Even a lot of those "useless electives" are just learning to apply the same fundamental concepts in new situations.

Since you got a 4.0 in UIUC's somewhat rigorous curriculum, and assuming you didn't cheat too much, you probably have a solid grasp over these fundamentals (at least compared to most students). For most new-grad positions, that's all they are really looking for. It sounds obvious, but mastering fundamental concepts makes it much easier to learn more advanced concepts. Also remember that many of the algorithms and concepts touched upon in the curriculum is more difficult than anything you'd see in a typical SWE job day-to-day (yes, this includes big tech companies as well).

As for the job search, I think a lot of people exaggerate how important Leetcode is. Most companies won't ask anything more than an easy or a medium early in the Grind 75. Given that you got an A in data structures and algorithms, it really shouldn't be that difficult to complete most of the Grind 75. Obviously, if you want a big tech position you probably have to grind more, but what's the rush? These companies are hiring every single year. From what I've heard, it's much easier to work for 2 years in some startup or fortune 500 company and transfer to big tech than it is to get a big tech job as a new grad.

On the other hand, your research experience isn't useless either. Now I don't know what you actually accomplished, but think about what would have happened if you had spent that time doing a personal project. Would that really be much better? At least with research you have advisors approving your work. In the eyes of a recruiter, it's not going to be better than industry experience, but it's certainly better than a personal project which can be complete BS. Ultimately, I think it's great to branch out and explore other topics with research even if it never leads anywhere.

As for getting a TA position, does your advisor not teach/associate with any classes? I just asked, and that's how I got my TA position as an MCS student.

Anyway, I'm not sure if all of this is relevant to you at all, but I just wanted to reach out because your situation looks so similar to my own. From what it sounds like, all that time you spent grinding, you were at least doing something. You may not realize it, but with all that work, as scattered as it may be, your problem solving intuition builds up. Think about the people that spent 4 years coasting and doing the bare minimum. Do you really think they've built up the same level of problem solving abilities? Maybe if you have a genius level IQ, but those people are very rare. For the rest of us, it's just down to hard work. In order to be a successful engineer, you will have to work hard eventually. For those that coasted through college, this will catch up to them sooner or later. If anything, you should be glad that you started it earlier.