Faster diode, like HSMS-2850 [1], and different leg lengths (tune for 5Ghz).

[1] https://datasheet4u.com/pdf-down/H/S/M/HSMS-2862_AgilentTech...

For 2.4 GHz each leg of the antenna should be 30 mm. For 5 GHz just under 15 mm.

See Dipole Calculator: https://www.omnicalculator.com/physics/dipole

And you need a faster diode.

Shorter antenna and faster diode. A Schmitt trigger would allow for much more sensitivity, but it would not be a passive device (requires a power source)