Still no keywords for photos in iOS?

No, adding keywords is still not supported.

And searching for keywords is now more limited on iOS 18 than it used to be on iOS 17.

When I added keywords on my Mac to my photos and synced my photos with iCloud Phots to my iPhone with OS 17, I could search for the keywords in Photos iOS and the search result would include a section "Keyword". This section is no missing. I will just a get a section with all photos containing the text of the keyword, which will include photos that contain the text, but not as keyword.

If you read all the posts on here, you would see why Apple doesn't.

But your point is well taken. Apple will read stuff left here:

Feedback - Photos - Apple

Sorry-- I was responding to "you would think that they would read some of the posts on here," being a bit sarcastic about many of the posts on this site. I can see why Apple doesn't try to read them. That's why they have a feedback site.