Recruiting rankings are important, but there are caveats all over that statement:
Some players are scouted more heavily than others. For some regions, it’s easier to gauge how a player’s talent level translates than it is in others (a particular problem for parts of the Northeast). There are a ton of three-star prospects and the differences between most of them are marginal. The same can be said for the low 3-star and high-2-star talent.
Players graded out at 4- and 5-star grades are the ones that are probably heavily scouted and have more tape on them, so those grades are at least more informed — though not a direct indication of whether or not that player will pan out for their chose school.