I will just for example look at the situation with materials. back then you had one renderer, that was completely stringent in its usage. then physical came. and maxon tried hard to implement it deeply. It was usable with the same UI, but even back then things started to get a bit strange with the reflectance chanel, which was and still is a whole material system on its own in one chanel of an other material system. then we got a node based Material system with a complete new Node UI, that was not integrated with the old layerbased. Xpresso still has the old UI and redshift that maxon bought has a material node system that can be used in the old expresso style system and in the new node look depending on what material you create.
You can say, that technology changed and that different renderers have different strength and weaknesses, and you are right, but all of these renderers have diffusion, emission, alpha, transparency and many more channels that they share and they have the same values to control but they all have different user interfaces. that means, that you have to learn different workflows to get the same result.