Yes, you can answer calls from your Apple Watch without cellular. However, you must have your Apple Watch connected to your iPhone via Bluetooth or WiFi in order for this to happen. If you are connected to your iPhone, you can answer calls from your Apple Watch even if it does not have cellular capability.
When a call is incoming to your iPhone, you can answer it on your Apple Watch by pressing the “Answer on Apple Watch” button. If you have an Apple Watch Series 3 or later with cellular, you also have the option to answer calls over Wi-Fi or your cellular network.