All modern glass made in the past 10 years vastly outperforms equivalent cost lenses made 20 years ago. What has changed the industry is computer aided design. A lens designer using modern tools can model the performance of a proposed lens design in an hour. In the old days the same work would take a week with arrows on paper. The glass itself has improved as well.
I have a couple of vintage Nikon fisheyes. Back in the day these were special order and Japanese customers were invited to the factory where their lens would be blessed by a Shinto priest. The cost then was over $10K in today’s money. You can get a much better lens for $200.
Zeiss lenses are not quite the same thing as Zeiss lens designs. The Leica outperforms Nikon or Canon on wide angle lenses because they are rangefinder cameras, there is no mirror sweep to contend with and it isn’t necessary to go for the extreme retrofocus approaches you will see on some of the DSLR lenses. My 8mm fisheyes have a huge front element, easily 120mm across. but manage only f/8. A modern SLR fisheye would be f/2.8. Same lens for a Leica would have a front element of no more than about 12mm and deliver f/1.2.
The reason the lens designers need to go retrofocus is to move the rear element away from the focal plane to avoid the mirror sweep. Sure a Leica is a better camera for wide angle landscapes but the lens designers have less experience with SLR. That was Nikon’s specialty. In fact back before the F1 launched, Nikon mostly made lenses for Canon cameras. The reason Nikon could introduce the first modern SLR was they were the only company with the lens designers.
