I am a big fan of saying "The rifle does not know which equipment you are using to aim it and it will shoot exactly the same shooting with open irons, quality peeps, 1-6x optic or 5-25x optics." But, the difference is your ability to see and aim precisely that changes with a quality optic.
You need to go to Africa and see what it is like today to hunt with iron sights. With some species or some regions, you will struggle to bag you game with irons if they run away everytime you approach to within 300y of the herds. Others will stand like cattle and allow you to walk right up to them and kill them. Neither experience is very sporting or much fun. 100+ years ago in the days of Roosevelt and Hemingway or earlier still in the times of Selous there were still unspoiled, relatively wild regions where game did not fear man as much and were present in much larger numbers.
Today with some exceptions, (unless you shoot like Quigley) I think you will find that hunting exclusively with iron sights only will be a very frustrating experience possibly leading to taking longer than advisable shots on game and also possibly leading to wounded game, poorly shot in some cases lost. Nothing sucks worse on safari that to think you may have wounded and lost a poor game animal. Take a rifle with a QD mount so you at least have the option to sully your rifle and your pride so, the game is in the salt instead of dying wounded in the bush.
Don't get me wrong, I also shoot irons some and even shoot some well enough to hunt with them. But, I do not do it often and I never do it when trophy fees are on the line. You do you.