At the end of the day, most modern clothing isn't made in brand factories.

It's subcontracted out to tons of shop, who then subcontract their orders out to even more shops.

Unsurprising that given such a system product varies.

Yes, and reducing the variation would increase costs. There are likely acceptability standards in play, but they are probably very lax standards.

They have been notorious for this for generations, to the point where it's sort of surprising to see it mentioned explicitly. Obvs this isn't a fashion forum and not everyone knows, but probably most people who want a specific pair of levis does know.

Do you wear them anyway, or return or tailor them or what?

I mean, they’re jeans and I live in New England. I will beat them to hell living in them and I am married. Sending them to a tailor feels funny!