This is debatable.
In the last few decades there have certainly been a steady stream of new steels introduced into knifemaking, however there are very few steels which are designed specifically for this job and most have some other primary industrial purpose, knifemakers just have to evaluate which of the steels available is most appropriate for the job.
It is also worth mentioning that simple carbon steels are more than adequate for most knives and the quality of design and manufacture is much more important.
Having said that stainless steels tend to be less effective knife steels, with the obvious exception that they are more corrosion resistant, so in this respect there is more scope for improvement. In particular stainless steels tend to be more difficult to sharpen for a given hardness which is why chisels etc tend to be plain carbon steel.
Historically the single biggest improvement was the advent of industrial mass production of steel as opposed to the various carburisation/decarburisation batch processes which were used before which depended greatly on the quality of the ore used and the skill of the smelter. Now you can buy a good quality tool steel with known and consistent properties off the shelf. So a lot of the more exotic processes like folding and pattern welding are more about getting a consistent product from variable raw materials than having much performance benefit purely in themselves.
There is also undoubtedly a certain amount of marketing hype and snake-oil in some of the super steels and expensive production knives.
There is also the fact that in certain sectors of the market achieving very high hardness is desirable from a marketing perspective as blades stay sharp longer, even if they are very difficult to sharpen and for inexperienced users edge retention will be seen as plus while they might blame themselves for an inability to sharpen them effectively.
From personal experience simple carbon steels are as good as anything as long as they are properly heat treated and designed although most bulk manufacturers tend to prefer stainless for cosmetic reasons. I would also say that once you get to the mid-range of the knife market it is often better to get a knife from a small artisan maker as you are then at least paying for a bit of craftsmanship and individuality.
Different knife makers and enthusiasts will have their own personal preferences for steels and heat treatments and in real terms it is quite difficult to get a 100% objective assessment of whether one steel is better than another. Often it is a case of balancing various conflicting requirements against each other and many of the newer commercial steel grades are designed to get a very specific set of performance requirements for a particular application.