Those who find the Rosary itself burdensome often get the short, barbed end of the stick in devotional literature. The Rosary is such a wonderful prayer, we might infer, all true Catholics ought to love love love praying it.
Yet finding the Rosary burdensome is not a moral failing. Good thing, too, since it seems to be relatively common.
What, then, can someone who dislikes praying the Rosary learn from praying the Rosary? In a word, discipline. Someone who pursues a spiritual good even though he finds the pursuit wearying will not be put off other spiritual goods out of sloth.
In general, simply knuckling down and doing good will erode the habit of doing nothing instead. And someone who is showing his love for God by doing something he doesn't enjoy will hardly be predisposed against showing his love for God by doing something he does enjoy.
Which is not to say that the Rosary is such a wonderful prayer, all true Catholics ought to pray it even if they hate it. I have always taken the "whatever works" approach to prayer, and if the Rosary doesn't work for you, then try something else.
But if the work you want done is to overcome a habit of sloth, then devotion to the Rosary could work, even if you never do obtain any other consolations from it.