BigClive covers this issue a fair amount on his Youtube teardown videos. It's not exactly built-in obsolescence, so much as being built to cost.
The cheapest way to build an LED bulb is to minimize the number of components. Instead of spreading the light emission out over a couple of dozen LEDs, it's cheaper to use a handful of LEDs but really overdrive them with high currents.
The result is a bulb that's cheap to make, but in ordinary use the chips and phosphors inside will run at high temperatures and degrade much more quickly. This effect will be even more pronounced with enclosed fixtures (like ceiling lights) that have little to no ventilation.
Manufacturers could design their way out of this by increasing the component count (spreading the light generation over more LED chips at lower current), but that's an expense that doesn't translate well to a brand or marketing claim. As it stands, ordinary consumers are unlikely to try to exercise their warranty on a bulb that fails after 1,000 hours rather than a rated 3,000 or so; there's no reason to expect that "this bulb is more expensive but will last a really long time" would make it in the consumer-facing market.
