How to avoid inappropriate ads in kids games on iPhone?

The age rating of the game also reflects the ads that the developer chooses to provide. If you find a game where the ad does not match the age rating for the game, then you can report that concern to apple here and choose the appropriate action for what you would like to do:

Report a Problem

You can also:

• Write a review in the App Store for that app describing your displeasure in the ads shown. This will be read by the developer and also other users looking to download the app.
• Report the issue to the ad provider. You can usually find the ad provider in one of the corners of the ads when you see them. There are really only about 5 different ad providers that are used by most games, with several other smaller companies.
• Pay the developer to remove ads.
• Or, of course, like you mentioned, delete the game altogether.

It is true that many game developers choose ads that are not appropriate for children and the game does have a 17+ rating to reflect that content, even though the game is simplistic enough for children to play. They do this purely for monetary reasons as that demographic of users are more likely to make purchases from the ads, where it may not be possible for children with Screen Time Restrictions.