Here are two widespread responses to Kant's categorical imperative. On one hand, one might note the absence of detailed rational derivation. On the other hand, even someone who maintains some skepticism is likely to have a sense that (nevertheless) there is something to Kant's central ideas.
The recommended solution is analysis of elements of the categorical imperative. Their appeal turns out to have different sources. One aspect of the first formulation rests on the logic of normative utterances. But others can be justified only in terms of their contributions to desirable functionings of a moral order.