As reported by Jonius here: How to unlock wild mode - #6 by Jonius-11264, the Blizzard shop wants people that “rank 25 or better” is required to open and use Wild packs.
That is of course no longer correct; the requirement is now Bronze 10 or better.
Here’s a screenshot I took to confirm Jonius’ claim after I read it:
https://imgur.com/a/xsqlpND