There is not an exact co-incidence between the label and the concept, as in almost any definition you can think of. Still there is a general utility in using those particular words. Certainly if you say yeshivish it will conjure up quite a different image in the listener’s mind than if you say modernish. Exactly what image will be conjured up will be somewhat different for each listener, still there will likely be a great deal of similarity as well, in most cases.
To argue that those labels have no meaning or are useless is ridiculous. To say that they are subject to misinterpretation, or they may have negative connotations, and/or they should not be used is something else.