There are systems in place for training and assessing to the minimum acceptable standard PPLs, FIs, schoolteachers, and for all I know duck-billed-platypus-sexers.
However, the reality will always be that whilst everybody has to meet the minimum standard when they took their test, some will then drop below that, and some will keep climbing to ever higher standards.
And an instructor with 1000++hrs of varied flying is likely to be more adaptable to what a student really needs than one with a couple of hundred hours on an integrated then an FI course, who knows nothing more than that book.
G