Lutron Caseta Pico remotes are not Zigbee devices. They use the Lutron Clear Connect protocol which differs from Zigbee, Z-wave, WiFi, and Bluetooth. The will only connect to other Lutron Caseta devices (and maybe the Lutron professional line). The Pico remotes are quite useful, if you have a Lutron hub. I even use them to control non-Lutron devices. However, I already have several spares.
I have gotten a lot of home automation stuff off Amazon. When I do a search, I might specify something like "Zigbee motion sensor". The search results displayed will include devices that are not Zigbee and devices that are not motion sensors. It is no wonder that people end up with devices they cannot use.
Since Harmony is being discontinued, but still supported, there may be an outlet for that.
If you have any of the Smartthings devices, they may be useful, but I doubt you got a deal on those.