Does it allow normal people get ahead through opportunity? I don't know because despite appearing that way it has always been manipulated by Cowell's agendas.
Does it find talent that otherwise would be missed because they couldn't find their way in? I think that's much more debatable as the show easily drops certain categories in favour of what sells to younger markets.
It's hard not to agree with the opinions of people like Example when they argue it overshadows greater talents going the traditional route in favour of a quick buck for Cowell.
I also think the chair challenge is very unfair. Unless the contestants are fully aware of the, usually blatent, attempts to up the drama it must be stressful & upsetting to be told you are amazing to then be ditched 10 mins later for what the judges already knew.