Not all stadiums are like this and the sun shines brightly. Is this a thing in real life though with Wembly? Never been there
Wembley can get some shadows, but it's nowhere near as dark inside as this makes it out to be.
For comparison here is a panorama of the ground that I took at the Spurs V Juventus friendly in August at around 5pm. So pretty much the same season and time that the game settings were.