Maybe we can clear things up a bit by drawing on a distinction from the world of "Positive Psychology," the field now being developed by Mihaly Csikszentmihalyi (Flow), Martin Seligman, and others: that is, the distinction between "pleasure" and "gratification."
Briefly, pleasure is immediate and requires no particular activity on our part of achieve it, while gratification is what we get when we get caught up in an activity that is challenging at a level that roughly matches our skills, so that we concentrate, lose ourselves in the activity, feel absorbed, caught up in a work well done. I gather this distinction is roughly equivalent to Aristotle's distinction between pleasures of sense and eudaimonia, or pleasures of activity, the pleasures of excellence [virtues, in the old sense] being exercised, although Seligman and Csikszentmihalyi derive it from actual research, rather than from rereading The Classics for enlightenment.
In any case, reading Hegel may not be a pleasure, but it could certainly bring gratification--and perhaps, once you know the Hegel well enough, it might bring a certain pleasure as well? (A sort of familiarity or reassurance, I mean, as familiar circuits of the brain are activated and we recall the gratification we once had. I get that reading Emerson sometimes.)
In terms of poetry, then, we might speak of
- poems that please me, immediately;
- poems that both please and gratify me;
- poems that don't please me but can gratify me, because they match my skills and catch me up in the activity of reading them;
- poems that no longer please me, or never get to, because I have grown habituated to the easy, immediate pleasures they offer;
- poems that do not gratify me because I find them too easy, not challenging enough to let me lose myself in the activity of reading them;
- poems that do not gratify me because I find them TOO challenging, which is to say that they demand skills I don't have, or don't care to exercise at the level they demand.
Examples of all of these cases to follow--but for now, it's time to switch gears and get back to my serious research project of reading romance fiction. Just finished The Sheik (1919), by E. M. Hull, the original 2oth century "I Love Bad Boys" bestseller and source for the famous Valentino movie. (Anyone remember Helen Kane's "He's up on his Latin and Greek, / But in his sheikin', he's week"? What song WAS that from?) Today it's The Devil's Cub, by Georgette Heyer, inventor of the Regency Romance. It's a hard knock life.