Most of the time, when mature fruits fall off or come off easily, they are ripe.
Have you tried keeping them for 2-3 days to 1 week in the house, and see if they ripen more? Pears usually taste best when the surface of the stem end gives to gentle pressure.
Try them at different stages and see if there is one that you like best... If they don't achieve good texture and flavor at any point, then I would guess this tree is a "dud"
...but you could most likely still make preserves like pear sauce and pear butter, and added flavor desserts like pear poached in simple syrup and wine / sherry / or port, or pear tart, etc.
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