I don't think Cristiano Ronaldo promoting something is doing that brand a disservice. It might not do it a service either, I certainly don't base my purchases on what Cristiano Ronaldo promotes.
It is a matter of superstars or celebrities associating their names with crypto businesses and the disaster that usually follows for the respective crypto businesses.
The matter is two-fold here. In some (better said, most) cases, the celebrities have no idea what they are promoting. Crypto is certainly more complex than a pair of underwear.
And if you don't know what you're promoting, you'd better stay away from it. In this sense, there is not much difference between crypto and the fiat world. If you promote some scammers or shady businesses the result is the same.
The only difference is more people understand the fiat world and are likely to catch onto the shady businesses, while crypto is still almost a virgin territory. When you explore it for the first time, you might meet some unknown plants or animals that can bite or poison you and you will make harm to that ecosystem too (we humans, are experts at that). You also may come across a plant, animal, or substance that could help feed mankind. I hope the metaphor is transparent enough that celebrities would understand it, although I doubt they read my posts.
The other aspect is about the crypto business itself. Even if it's not a scam, it's a serious business, can it handle all the extra attention that comes from the endorsements of major influencers? If it's not built on a very solid foundation, it might not.
Binance is as solid as it gets in the crypto sphere, from all data available publicly. Except it's centralized and it has a way too dominant position in the market, and CZ is aggressively trying to increase it by publicly forcing stress tests into its competitors, during hard times. All for the good of crypto, of course.
This is just one example of Binance dominance, taken from one of 
Note the chart includes both CEXes and DEXes.
Regarding Cristiano Ronaldo and Binance, he launched his first NFT collection on Binance 2 days before the World Cup started. Very good timing considering the WC, very bad timing considering that NFTs without use case lost all shine, and with it their value.
I probably saw the news about his collection but forgot about it in the meantime. What reminded me was a TV commercial I saw before or during the break of the game between Spain and Germany.
The commercial is made in a way that promotes Binance at the same time. Therefore my title. We have the ingredients. Superstar promotes crypto business. Will this time be any different?
I hope so because otherwise, I believe the crypto world will be scorched. Much like Russia dropping a nuke on the world (unlikely), given the tentacles of Binance. Some crypto projects might survive, but much like a nuke, this would be a before-and-after event.