If you cannot wait, you can already substantially reduce the transparency effect via Settings -> Accessibility -> Display & Text Size -> Reduce Transparency.
This new setting and the existing "Reduce Transparency" look a little different but same idea overall.
There were/are some horrible bugs with Reduce Transparency mode in iOS 26, let's hope this new mode gets added to the fully-tested set of configurations.
I’ve found “Increase Contrast” to be a better setting. Still a little bit of transparency but most elements now have borders and much more readable text. Not too many rough edges.
This new setting and the existing "Reduce Transparency" look a little different but same idea overall.