It's like a movie critic cannot criticize a movie, since the film-maker can just state "why don't you just make a better movie?"; A diner cannot criticize the chef because chef can say "why don't just prepare a better meal?", etc..
Bringing the personal into it is unrealistic since not everyone is equipped to be a movie maker, chef or entrepreneur but that doesn't mean those jobs are immune from criticism.
Even Warren Buffet has spoken about the excesses of capitalism and pointed-out that the rich are taxed too little as just one example of capitalism's flaws.
Capitalism is still the best system but that doesn't mean it's perfect or can no longer be improved.