You're making what is simple into something complex. Look at fielders/batters who play into their mid to late thirties. Then, look at their peak years. Pretty basic.
The answer to the problem you cite is to, a. scout and coach very, very well and, b. accumulate that excellent young talent instead of throwing it away in semi-desperate trades (e.g., Tucker). At the end, I'm not worried. It isn't me paying Bregman as he gets grayer.