i like your post. my tiers are a bit different
tier 1 - duke, unc, ku, kentucky, uconn, ucla. duke has more titles than anyone since 1991. they are definitely tier 1. ucla has a combined 9 elite eight and final 4 appearances since 1996. that's one appearance every 3 years on average. uconn has 3 titles since 2004.
tier 2 - nova, michigan state, baylor, michigan, UH, gonzaga. jay wright is retired and is why i don't have nova in tier 1.
tier 3 - florida, louisville, . when guys like billy donovan and pitino leave, their programs inevitably fall off. not even sure if this tier should exist and maybe they should all just be lumped in with 'next tier' instead. however, florida and louisville have fairly recent titles.
next tier: teams like ohio st, Texas. i agree with what you posted, p5 teams and mid majors that consistently make the tournament are in this tier. I would add, a lot of schools are in this tier. ohio state had a pretty good run from 2007-2013 but hasn't sniffed a sweet 16 since 2013. we haven't been to a sweet 16 in 14 years.