Nowadays vehicles are so complicated, with so much technology put into it, and cannot increase the price, failure in certain area is expected.
FOr a Sienna with 268 HP and all the power doors, AWD etc..., if Toyota need to make it with perfect quality, it will have to use Lexus's level of materials and QA control, and the price for the van will be in in the 50K (for the base model) to 70K range for the top model.
They need to save cost, so they cheap out with a rubber hose to carry hot engine oil to the dual VVT-I, use a cheaper motor in the power doors etc.. ..... to save a few bucks here and there.
Too bad that we can no longer buy a basic vehicle that will last a long time, like the 90's corolla. Even today's Corolla gas pedal failed. My colleague family owns a 2000 Sienna XLE, with a power sliding door, the door never failed, engine is running fine (no VVT-I), millage is also 200K-km already. We will never see this happen again on a 2007 or newer Sienna.