You appear to be confused about ECs. They don’t necessitate that you join social clubs at all. Naturally surfing the net, playing video games, wasting your time googling nonsense, watching mindless youtubes or watching TV won’t be ECs that colleges view as valuable. But they are ECs. There are many ECs that colleges find valuable but that don’t require socializing. If you spent your spare time on useless time wasters, well then you are right, competitive colleges won’t view your activities as valuable. But don’t suggest that social anxiety is to blame for that! There is too much of a disability climate developing among young people who seem to think blaming psychological issues excuses almost anything.
GA Tech and UIUC are both top shelf CS schools not a bit beneath the ones you list above it. They are not less competitive.
You are correct that StonyBrook is “insanely” cheap thanks to NY tax payers, poor resources, retro salaries for staff, and a retro approach to academics at SUNYs. But that does not mean that " the only reason to go anywhere else is if their CS program was significantly better" because the entire experience at another school might be better. SUNYs are hopelessly behind the times although Stony Brook is probably the best of the university centers.
Virginia Tech is a far better school for CS and engineering. I am not saying VT attracts better students. Differentiate please. I am saying that it offers a better experience to the students who attend than does any SUNY. Anyone who has spent a week (maybe even a day) at each campus would have to agree. I would not look at VT as a safety in CS. You can’t simply infer from overall acceptance rates what the rate is for specific fields. But VT, Madison, Purdue… are all outstanding but will be both expensive and difficult to get into. You have not provided your credentials but they are competitive programs for CS. They will all provide a better education in CS and overall than sUNY-which (again) is not to say that the students are stronger. Just that the schools are better.