I think Chanel has gradually let off their quality standards for one reason: they can.
Once upon a time, luxury goods like Chanel handbags and RTW were the exclusive province of the affluent and outright wealthy. These people spent plenty but had high standards: a sweater, bag or pair of shoes was expected to last. They stocked a wardrobe, not an exhibition, and very few were purchasing multiple flaps in a single shot.
Likewise, when Hermes created the Birkin for its namesake, the notion that a customer might collect dozens in myriad colors, leathers, and sizes would've been considered insane. Once you bought one in your preferred color and size, why would you need another unless the older one wore out? It's Hermes, you only need the one.
Today, fashion houses have become little more than bling purveyors. The top 10% buy for the sake of it, to have the latest and newest, and to show off. When a woman has 100 bags, who needs quality? She won't use any of them enough to notice or care. The brand value matters more than the actual object, and our attitudes toward consumption today reflect this in every way.
Designer bags are no longer little everyday luxuries that make our lives a little happier. They are a massive "collection", an assortment to be maintained and displayed like badge of our material success. In the end, Chanel is merely playing an existing zeitgeist to its profit, not creating it.