If we have the debate between this year's team and the 2021 team.... firstly, just as disclosure, I can almost feel one of the arguments for the 2021 team being the "refuse to lose" saying that's been thrown around here ad nauseam. While I have utterly no clue what that refers to, and on the other hand this year's team has the more well-rounded metrics (which does not account for recency basis or pessimism depending on which side one is on), I do think ultimately what we should look for is resume over the metrics (because, let's be honest, both teams are extremely talented, and ultimately it comes down to who you beat).
To start, that team didn't have nearly the non-conference that this team had. Yes Baylor was incredible, but Duke (whom we beat) was awful that year, and we also lost to Missouri.
Where we really made our mark however was conference play. I'd argue the B10 that year was just as, if not even more stacked than this year. The four "tier 1" teams that were clearly above the rest of the league were: Illinois, Iowa, Ohio State, Michigan (as a sidenote, I think Illinois, Michigan, Purdue, Nebraska can rival that this year). We went an astounding 5-1 against the other three teams, lone loss being to Ohio State, which was influenced by a horrible missed call at the end.
Overall we finished with just 6 losses (pre tournament) and won the big ten tournament. There's just so much value in hanging a banner IMO.
So, just looking at the regular season results (not counting tourney.... yet), for me the bar to beat for this team to be considered in the same hemisphere as that regular season would be a) hang a banner, tourney or reg season and b) get AT MINIMUM a 2 seed, which would mean a max of 7 or 8 losses (again, 2021 team finished with 6).
Now we get to the tournament aspect. This is the hardest part to judge because it comes down one, super subjective thing, and that is: by how much more does one weigh tourney success over regular season success. It's a one and done game, and lots of Cinderella teams advance, and great teams lose. It has almost NOTHING to do with how great of a team you are, but EVERYTHING to do with how your season is perceived.
A person who claims they live and die by the tourney would likely conceed to say 2022 Michigan -- who were ranked #6 preseason, had an insanely disappointing year, made it in as a 11 seed, but made a S16 -- is a more successful year than 2021 Illinois. They'd almost certainly claim 2024 Illinois is more successful than 2021 Illinois.
IMHO, if the discussion will reign to be who's THE BETTER team, the tourney is far from the make or break deal. If it's about which is the more successful season, then it's by far the biggest qualifier. But since our team this year and the '21 team are both talent wise very potent.... if we make it in this year as a 2 seed, make a final four, whereas that team was a 1 seed but lost in the 1-8... almost certainly people would say this team had the more successful year AND is the better team. FWIW, I think the '01 Illini were a real talented bunch, but don't even get mentioned with the 2005 and 1989 teams since they don't have the F4 to show for it.
All in all, time will tell the fate of each season in comparison to its past teams. I feel like the '21 team was super top-heavy offensively with Ayo, Kofi, Trent, etc. This year's group, in contrast, could have all 5 starters average double figures, but no one guy average 20 -- kinda like UCONN two years ago. At the end it evens out, probably by a hair in favor of this year's group. The '21 team was super stout defensively however (number 7 in Kenpom in AdjD).