It’s more than just a rectifier. LEDs of any type, white or otherwise, require regulated current, not just any voltage, otherwise even an LED will burn out. Vis-a-vis: cheap white LED flashlights that take 3 AA or AAA batteries; there’s no current regulation, they just call it ‘close enough’. Over time some of those LEDs will fail and start flashing when they heat up. So what usuall fails in white LED bulbs in your house is the electronics responsible for regulation. Sometimes the LEDs themselves (of which there is usually more than one LED, they’re usually an array of several) will burn out, killing the whole bulb. I have a 1080p TV that the backlight went out on it after a few years use, which I replaced myself. Inside it are three circuit board strips with white LEDs on them, all wired in series like christmas tree lights used to be wired. All it takes is one of them opening up and the whole backlight stops working. Anything like this that is manufactured at massive scale is bound to have some failures, and white LEDs and white LED bulbs are no exception.