Nurb said:
It's not a nitpick, the "Hotter! Younger!" direction of reboots is a big issue, especially when trying to make people look like scientists.
Except it's not really "hotter! Younger!" here, is it? Reed was 21 in the Ultimate comics, and mid twenties in the original comics. The only person who was likely to be older in the first place is the guy who will probably spend the movie either in a CGI suit or a foam rubber rock costume, and even then, I don't think he was supposed to be significantly older than Reed.
The fact is, this is older than you think. Reed, Ben and Johnny were all youthful prodigies of one sort or another, and Sue was portrayed as still a kid when she took interested in Reed. This is discounting the Ultimates origin, because it demonstrates how far back the idea of them as youthful.
And that's exactly why it is a nitpick. A poorly chosen one at that. It's like complaining that Sony decided to make Spider-Man a teenager or that Fox decided to capitalise on Nazis by making Magneto German.
The casting here may end up being the most authentic part of the movie.
...Given the supposedly plot, that includes Michael B Jordan.