Can Webcam be replaced?

Well… I would first check the T-CON cable connections look at Step 24 in this guide MacBook Pro 16" 2019 Screen Replacement the two silver metal brackets hold the four ribbon cables one of the two smaller cables is the camera connection see if there is any damage or corrosion around it. I’ve managed to fix one when th a bit of cleaning.

Otherwise you really can only replace the full display as Apple really worked hard in making it very hard to open.

Maybe you should just use your iPhone (which you can do with the newer ones) or other Bluetooth to USB camera.