Voltage shift 5V to 3.3V for PIC16LF145x 3.3V I/O input, several approaches
With resistances this high, many parasitics become concerning. You've highlighted one, input leakage current, but another is any dirt, flux residue, oils etc on the PCB, which can have resistances in the tens of megohms range, or even much lower if it's wet.

0.4 microamps is not a lot, even compared to the MCU's idle power consumption. You can probably stand to make this significantly less stiff and still consume minimal current, while having to worry less about the cleanliness of your PCB and other parasitics than you otherwise would.

Regardless of these concerns, the power drawn by the divider is drawn from the VBUS supply, not from your device's power supply - so power consumption should not be so pressing a concern here.