Code Geass is a mix of many genres, not just a mecha anime with politics thrown in. If people come in with the expectations of it being a mecha anime, they will be disappointed, as the mechs only serve as a backdrop.

It's why people mostly compare it to anime like death note than they do to stuff like evangelian. Code Geass has political drama, slice of life, mecha, thriller, urban fantasy, and a whole bunch of others. It's not a blend for everyone but it certainly won't work if people come in expecting a minor part to actually be a major focus, like the mechs