How can I stop Crypto scam ads on my iPad Safari?

You are correct that the ads are being brought to you by the Developer of the game where they are receiving money from the Ad Network they are using. Apple does not provide any ads in games and does not receive any revenue from them. You have many options with the first being to contact the Developer like you have done, and also:

• Write a review for the app in the App Store, alerting other potential users. Many times this will get the attention of the developer for a quicker resolution as your complaint is being seen by everyone, where contacting the developer is seen by them as only a single complaint.
• If the app has an in-app purchase to remove ads, this may be an option for you where you will not see them.
• Contact the Ad Network used by the Developer. You usually see the name of the agency used in one of the corners of the ad. Feel free to post that Ad Network here as many games may be using that same Ad Network where those same ads are seen on devices from other manufacturers as well.
• Report the Ad Network to your local consumer protection agency.
• Go to reportaproblem.apple.com and one of the options for reporting is to Report illegal of offensive content.
• Quit playing the game. That is the ultimate way to no longer support a developer where they are profiting by you playing their game and you do not agree with the content you are seeing.

Note that there is a difference between what may be reported as a scam by the media and what is actually illegal. There have been many reports of scams on Facebook Marketplace, yet it still exists and not illegal, but the media would be correct in reporting those scams. Other grey area topics are Antivirus software, VPN marketing practices, and even Reverse Mortgage ads promoted by many celebrities. Personally I think all Crypto is a scam, but it clearly is not illegal.