At 40 years, there is an expectation that the rubber and most plastic components have become embrittled. The hinges likely only wore out after the spring had reduced function (and lack of lubrication)

After your weld, I hope you consider replacing all rubber with silicone, and add lubrication to at least an annual list.

The plastic and rubber bits are absolutely fine.

The hinges broke because someone leaned on the door with their full weight while it was open. The grease on the hinge pins was perfectly okay too.

Ariston used to be a quality company.

i replaced few years ago dishwasher that was at this point of time 20 years old (GE). When it was removed from below countertop plastic connector on top of dishwasher (water hookup) fall apart into dozen of small pieces.