As a finnish person, I've never heard of anyone who is "done" with the Moomins.
Everyone who knows any of the characters, loves them. People who don't are either indifferent or find the designs immediately appealing.
But basically everyone here either thinks they're "neat", don't mind them, or adore them.
It's kind of incredible how inoffensive they manage to be, while at the same time the stories Jannsson wrote tackle some very serious subjects.
In Finland there is an air of respect towards the franchise, and deference towards the wisdom within the stories.
Merch is usually made with real attention to quality. The mugs in particular aren't cheap, and when taken care of, will last longer than their owners. Even when regulary used.
Though I do find some of the branding of consumable goods to be quite crass, and I can't say I see anyone buying the stuff... I suspect it will fall flat with most people, and soon stop being a thing.