If it's a historical book it's different. but if it's supposed to be based on the present or near-present, the real name for a figure can date the book very fast.

^

Well, if it is someone who has very distinct characteristics and couldn`t really be confused with anybode else, they rather should be left with the real name. Otherwise it will be very cringey to read anything about it. Only exception for this would be if the story is happening in an alternate universe where no one of the characters is taken from the real life. And only if e.g. the writer for some weird reason really likes character traits of the US president, but in their book the person with those exact traits isn`t a president of a large country. Then it`s ok.
And it works vice versa. When writing about present times and describing exact people, it will seem very weird if popular people will have their names, but will have totally different characteristics as irl. Then it is better to set the story in an unknown time period in future or just some other universe with 100% fictional president, celebrities etc.

I would usually prefer them to use the real person, but there are a lot of hilariously designed fictional characters out there who are parodies of real people, and I have to admit I love that sort of thing. XD

Parodies of real people are the best lmao.

I'd like it! I'm not too concerned about the real-life people and (when they're mentioned in stories) I usually get clueless about the inside jokes, memes, political matters, etc. When you've got fictional people, you don't need to worry about that trivia. Everything's in the story. xD