Why do so many microwaves seem to die after 2 to 3 years?

Across r/Appliances and r/BuyItForLife discussions, the consensus is that modern microwaves are built to a much lower price point than units from the 1990s, with thinner cavity coatings, cheaper door switches, and plastic handles that crack. Inverter models from Panasonic and Toshiba, and older Sharp Carousel units, come up most often in long-life testimonials. Buying from a retailer with a generous return window (Costco, Best Buy) is the most-cited hedge.