I think that despite all his flaws, BK showed that this team could be a playoff-type team.
And I think the expectations for Freeman are so high because they hired him coming off those BK years, and the fanbase expects that train to continue. The risk of Freeman's hire was that he absolutely seems to be the guy who could recruit at a higher level, which may in turn lead to playoff victories...but you also run the risk that he doesn't offer the continuity the fanbase expects and the program takes a step back because he isn't the same experienced lifer that BK was.
Effectively, it's the fanbase saying "this is where we expect to be, so you better not hire someone who messes with that standard." This, to me, is the macro issue (and the source of my frustration sometimes), but also ignores some micro-level crap going on behind the scenes that may have been mitigating factors in the "we expect playoff appearances" mentality BK gave the fanbase (like his failure to maintain any semblance of elite QB play, his rough tendency to lose against highly-ranked opponents in spectacular fashion - Clemson in the ACC 'ship, Bama and Clemson in the playoffs, Miami 2017, Michigan 2021 - and his lukewarm approach to recruiting) that cuts against the "Freeman inherited a well-oiled machine!" narrative.