Structured, well thought-out training plans can make a very big difference in your fitness and riding ability. Just how much improvement you will see depends on many things including your inate capacity. However, as I read your post, I wonder why this is something with which you are concerned. There are many reasons people ride, and thoughts about others who ride faster, harder, etc. than you may be a helpful motivator or dysfunctional idea that keeps you from enjoying your riding as much as you might. I'd strongly suggest that you think about why you ride and want to continue riding and then set some goals based on what you really want. If riding faster, harder, longer, etc. is what you really want, then rigorous training plan will make a difference. A caution.... keep in mind that many people make the mistake of over training and forget to take rest days. If you do a general internet search for training plans for older cyclist, you'll find lots of them from which to pick.