There's nothing generically wrong with older bikes. What's the major improvement with newer ones? Fancier steels that shave a few ounces of weight and maybe got a little more stiff at the expense of reliability? A more modern groupset that gives 20 speeds instead of 10 with more convenient but less reliable brifters. You can pick up nice, vintage 531 frames made by good welders at cheap prices, nicely kitted out with old Record stuff that isn't the fanciest these days but won't quit. And they're only gonna run you a couple hundred bucks. At the same time a lot of junk from around the same vintage will sell for about as much. It helps to know what you're looking at.