For centuries children and adults did ok treating cataract with home remedies. Why can't i?

Not true . There are no known 'home remedies', natural supplements, or medication with any proven efficacy in treating cataracts. Currently the treatment is observation, refractive correction (glasses etc) until surgery is indicated. I'm hopeful that, in the future, non surgical treatments will become available to this common condition.
It doesn't work. Cataracts are the natural lens of the eye that get cloudy with age. When they get cloudy you can't see well through it. There are no topical or oral treatments that can restore the translucency of the lens. The only way to regain sight is to remove the lens. Cataract surgery is very common, very safe and works very well.
Who says you can't. If they are worth consulting ,they would certainly recommend the most effective treatments available. You are free to do what you wish as long as the courts still find you a competent person to make such decisions. You can embrace any treatments that were prevalent in an age when people seldom lived past 50. You would need to accept responsibility for any impairment resulting from your choices, but they are yours to make.
Cataracts. N-acetylcarnosine (NAC) in small studies showed improve vision in cataract patients. However, it has not been studied in double blind, randomized, prospective way & studies were paid for by company who has vested interest. It is not FDA approved. Likely sun protection & eating a diet rich in antioxidants is just as good; so there is still not enough proof. More info at: eyedoc2020@blogspot.com.
Home remedy x cats. It is impossible to cure cataracts without surgery. What is possible is to prevent them. What you mentioned probably was an misinterpretation or misdiagnosis of the disorder of the eyes. May be pts had pterigions, conjunctivitis, keratitis or other diseases that self-repaired themselves and equivocally it was attributed to "home remedies ".
They actually didn't. Children always did badly as the cataract in this age group prevents proper development of vision. Adults spontaneously can improve with liquification of cataracts and some visual restoration (taking many years) - the basis of many biblical "miracles". An old technique is "couching" - purposeful dislocation of the cataract. Modern removal is so much better that we are in a golden age for this.