does science tell you your right? First off what is "old steel" Stainless steel for example was invented in the 30's. D2 first used in the 60's. The cost of a modern knife compared to an old knife has to be calculated to adjust for inflation of the dollar before worrying about buying a "brand" doesn't it?
Acording to the us inflation calculator( https://www.in2013dollars.com/us/inflation/1975?amount=1 ) the average is 3.62% per year since 1946. lets look at a knife from 1975 avg inflation of 3.67% or 1$ = $5.64 so a 20 dollar knife in 75 would cost in todays world $112.80. So how much did round knives cost in 1975?
Ultimately the important part about knives is the hardness and tempering process not the steel or when it was made. There were old knives that sucked and there are new knives that suck due to that fact, and all made from the same steel formulas. On the flip side are old and new tools that are good also.
Scientifically there is no difference in the steels, nor the hardening nor the tempering. Time or age has nothing to do with that. But there is a difference in how it was done and by whom it was done. Stricter manufacturing tolerances for example and more human interface in older tool work led to better overall tool quality than modern standards in most cases. Today you can buy a knife from several different companies all with the made in china stamp right on the side, if they are bad they will gladly send you another, why because times are different and a product line doesn't reflect the company in the same way. Folks have learned to settle for a replacement so construction standards have changed, make bazillions of product then replace the bad ones as they are found by the consumer is the new process. Selling higher quality tools that pass stricter standards so they aren't sent back is the old process.
Science and technology in itself has changed drastically in the last few decades from producing a higher quality product for the consumer to producing a higher bottom line for the companies that fund the research, which means quality is simply not always the target point.
Old tools are an excellent find and well worth it if they aren't worn out, that's the key to buying old tools especially knives.