Honestly, you never could do this. The human eye, even a young one, is incapable of focusing on two object simultaneously. What you have lost is the ability to rapidly change focus from one point to another. This happens to everybody as they age.
Cataract surgery is fine if you need it, but the problem may be simple aging, not cataracts. I've always worn eyeglasses for distance vision, but it never interfered with my shooting until about 10 yrs ago. My distance vision is still fine if I'm wearing glasses, but I need bifocals for reading and close vision now. Without bifocals, I can't see the gauges on my dashboard clearly, and more importantly, the front sights on my shorter barreled rifles now appear blurred. An example would be Winchester 94, Ruger RSI, and most of my .22's (dammit!). The front sight on my full length rifles is starting to blur as well, and I expect this to get worse over time. When I was young I taught myself to shoot with the backsight blurred, focusing on the front sight and the target, but now I can foresee the day when all my rifles will need to wear glass if I want to keep shooting.