For example, there is a new style of shoe, and when there are only a few people who wear it, it's hip and trendy, but now everybody has a pair and it's ______. Or, there's a new and popular product that has a stupid sounding name. It's so popular and the name is said so often that the name doesn't sound stupid any more. The name has become _______.
... but now everybody has a pair and it's passé:
[PREDICATIVE] 1 No longer fashionable; out of date:
miniskirts are passé—the best skirts are knee-length
The name has become a cliché:
1 A phrase or opinion that is overused and betrays a lack of original thought:
In the same way that an overused phrase inevitably becomes a cliché, a recurring joke sooner or later loses impact.
The name has become banal:
So lacking in originality as to be obvious and boring:
songs with banal, repeated words
Often people say such a thing is over-exposed.
The word you're looking for is blasé:
Blasé: unimpressed with or indifferent to something because one has experienced or seen it so often before
I would say that the thing is saturating/saturated
- run of the mill
In order of general popularity:
Pretty cool question: a single word that has negative connotations for trendy elitists/vocabulary pedants and positive ones for the rest of us.
"Popular" comes pretty close, but it sometimes requires context, because something can be/become popular within a small group/subset of the general population without enjoying widespread popularity / acceptance.
“Popularized,” on the other hand is more context-neutral, having the notion of “widespread” (another option in itself) built right in it (popularized: adjective - enjoying widespread favor or approval) (widespread: adjective: common over a wide area or among many people).
...but now everybody has a pair and it's [become] popularized / widespread.
The name has become popularized / widespread.
If you're open to paraphrasing, I suggest fatigue
From Oxford (sense 1.2)
[WITH MODIFIER] A lessening in one’s response to or enthusiasm for something, caused by overexposure.
Maybe this doesn't fit your example sentences, (words that fit have already been suggested). This fits your title, though. This describes “When there's too much of something and people don't take interest anymore”
Too many superhero movies may cause genre fatigue among audiences.
I think Desensitized sums it up pretty well.