You can buy appliances which will last that long, but they cost a lot of money. The reality isn’t that people forgot how to make things durable, it’s that consumer demand is so conditioned by price, most people “prefer” to spend less on appliances they will replace more often.
The average appliance these days is actually significantly cheaper when adjusted for inflation compared to the 60s and 70s.
The biggest point is that all the supernatural stuff is either outright debunked or left slightly ambiguous which really supports the whole “I want to believe” vibe throughout the entire run.
That is, until the final episodes where they invent, and explicitly demonstrate, some idiotic bubble universe for abused children, which might be the dumbest way the show could have possibly ended.