First, I would never rely on the college evaluator website or any 3rd party website except US news/Washington Monthly/Forbes. Sometimes they're accurate, sometimes they're way off because of the way they collect and report data - they don't get data directly from the institution. Second, acceptance rate is really irrelevant - it doesn't tell you anything about average GPA/SAT/ACT because different students self-select into applying, and yield rates are different. The US News College Compass tool has equivalent data for all campuses, but I didn't pay the $40 for access. The data below is according to each institution's own admissions websites and includes data from the class profiles for the 2021 entering class, with the exception of Rutgers and Nebraska (just not reported in the same way). Nebraska's is taken from a less reliable source, so take that with a grain of salt. Rutgers had data available for each college but not for the university as a whole.
But, looking at the entering 2021 freshman class data:
1) Admissions to IU was tougher than admission to: Nebraska, Michigan State, and Purdue (very close to Purdue, but a tick tougher. Boilers will never believe or admit to this even though it's from their own website).
2) IU had the same entering average ACT score as Wisconsin but a lower average SAT score.
3) IU had the same middle 50% ACT score as Minnesota but a lower middle 50 SAT score
4) The classes at Ohio State and Penn State had middle 50 ACT scores 1 point higher than IU.
5) With the exception of Northwestern and Michigan on the high end and Nebraska and MSU on the low end, the rest of the schools are admitting similar students, with marginally differences really only in the 1-2 ACT point range.
6) IU has a higher middle 50% GPA than most peer institutions that reported it, but they're all very close.
School | Middle 50% GPA | Average GPA | SAT Middle 50% | SAT Average | ACT Middle 50% | ACT Average |
IU | 3.62-4.0 | 3.9 | 1230-1420 | 1322 | 27-32 | 30 |
Illinois | 3.58-3.95 | | 1330-1510 | | 29-34 | |
Purdue | 3.5-3.9 | | 1190-1410 | | 26-33 | |
Ohio State | | | 1330-1460 | | 28-33 | |
Penn State | 3.59-3.93 | | 1270-1450 | | 28-33 | |
Rutgers** | - | - | - | - | - | - |
Maryland | | | 1360-1500 | | 29-31 | |
Wisconsin | | | | 1417 | | 30.1 |
Nebraska** | | | | 1240 | | 25 |
Michigan | | 3.9 | 1400-1540 | | 32-35 | |
Michigan State | 3.5-4.0 | | 1110-1310 | | 23-29 | |
Minnesota | 3.5-3.96 | | 1330-1500 | | 27-32 | |
Northwestern*2022 | | | 1460-1540 | | 33-35 | |
Differences in admissions criteria between IU and the middle/top of the conference were way more pronounced 20 years ago than they are now. Looking at the 2021 class, IU looks like a standard B1G school.