Lot of issues here. Are fermenting rooms mechanically cooled today to ensure a stable temperature for top-fermentation? (I understand all bourbon is top-fermented at more or less ambient temperature as opposed to refrigerated bottom ferments lager-style). The warmer the ferment, the more estery (fruity) it will be...
Fermenting vessels today are generally of metal which can be cleaned well and avoids microorganisms which lurk in the wood which no amount of lime treatment could clean 100%. In general, I believe fermenting systems are technically sterile whereas surely this was not the case 20 years ago and more. Of course, this is a good thing, but one wonders if idiosyncratic flavors resulting from a "live" plant may be a thing of the past (at any rate in the large modern plants).
Yeasts today surely are better controlled and "cleaner" than in past decades. Again, flavor will be clean and more predictable, but will it always be better?
Add to all this the numerous points addressed in other threads (mash ABV, distilling out and entry ABV, mash thickness (addressed in a thread last year on the other board), age of wood used to make barrels today, etc., and one can see it is almost inevitable that bourbon palate will change over time.
Change is not bad as long as overall quality does not decline. I don't think it has but unquestionably I think, certain tastes are lost to history due to the particular nature and approach of plants long closed or torn down or simply adopting new processes and equipment over time. The rich rummy bourbon of 1970's Benchmark or Beam's Choice, the fruity Old-Grandad of the 80's and earlier, the perfumy and sometimes butterscotch-like palate of Old Taylor of decades past, these are tastes that seem of a past time.
However, the task of distillers today is to replace these with tastes as good or better. And there are many examples, we discuss them all the time.