> Ask inventors, who are supposed to be the beneficiaries of the law (at least for patents).
While this is a common misconception, inventors are not the intended beneficiaries of patent law. Patent law is supposed to benefit the public, by incentivising invention and encouraging inventors to publicize the workings of their inventions. Benefiting inventors is only a side-effect, not the goal.
(How well it accomplishes that goal, and whether the cost in liberty was justifiable in the first place, are debatable; however, that is an argument for another time.)
While inventors may have some input to offer on the effectiveness of any given incentive structure, it is the public which pays the cost of these patent monopolies, ostensibly implemented for their benefit, and which should have the ultimate say regarding both their existence and their form.