A lot of things have changed. Once real slide shows were abundant; now you can't even find a lab which will mount slides.
Yes, I used to project slides. Then I stopped projecting slides and started printing slides. That was in the 1980s.
Once many landscape photographers shot 4x5 for sake of publishable stock photographs;
I never met anyone who shot 4x5 landscapes for stock. I am sure some did. Who they are is likely unknown.
...now most people are content with viewing color images over the web, with little concern for accuracy.
...before most people were content with viewing color images in photo albums, with little concern for color accuracy. The more things change, the more they remain the same.
Others like me shot various 4X5 and 8X10 chrome films for sake of Cibachrome prints.
I made Cibachome prints from slides too. I ultimately decided that Cibachrome prints looked too plasticky and went back to black and white on fiber based papers, and now alternative processes.
At that kind of effort in the wilderness, and expenditure in dollars, one doesn't gamble by guessing or listening to rumors.
To no one's surprise, shooting large format is expensive so it helps to know what you are doing. Of course, everyone was a beginner at one time.
And you rarely have the luxury to bracket anything; the first exposure has to count.
I don't know why you can't bracket landscapes. The trees and rocks aren't going anywhere. You can flip the film holder pretty quickly. Ansel Adams routinely made two exposures. Of course, if you are confident with your metering skills, you don't need to bracket.
Underexposing E6 products a little bit might have make them look better projected or over a bright light box, but also makes them harder to reproduce in print or publication fashion, especially so with Velvia, which is very high contrast to begin with. People need to state their objectives before blurting out this and that.
Since slide shows were, as you say, abundant, it made sense to underexpose a bit. The other upside was that it protected against blown highlights. Blown highlights don't look very good in Cibachrome prints.
And those of us who of necessity had to control the variables ourselves very tightly, and had the instrumentation to do so, can appreciate the tremendous level of manufacturing quality control offered by both Fuji and Kodak for decades. They know what they are doing.
To no one's surprise, Kodak and Fuji make good films. And I am not even sure what "of necessity had to control the variables ourselves very tightly, and had the instrumentation to do so" means in the context of developing color prints in tubes. Are you talking about using a timer, a thermometer, and a roller base?
If Kodak has had financial troubles, that had more to do with bean counters and egotistical management types who did not rise up through the ranks of actual manufacturing skills, but were dropped into the top from unrelated backgrounds. That kind of thing was a plague in the 90's and early 2000's, and crippled many previously strong manufacturing corporations, not just Kodak.
Businesses are run by people. People make mistakes. Sometimes disastrous ones. Even people who were working in the manufacturing area and promoted to executive management make mistakes. Running a coating machine well doesn't assure success in orchestrating a financial restructuring.
But since this is all being debated on what is supposedly the Color Darkroom section, just how many of you are actually doing that, and printing your chromes in the darkroom, or in the past have done so, one way or another? It can make a huge difference with respect to how such opinions are formed in the first place.
As I mentioned above, I haven't shot and printed slides in quite a while. Doesn't mean I don't know anything about it. My memory is largely intact. The learning curve is a curve, not a straight line, so after a while, doing the same thing over and over again doesn't yield any new insight or improvement. You might even get stuck in a rut. So don't confuse how long someone has been doing something with how well they are doing it.
Some photographers go to extremes to make things as complicated as possible, or at least to make what they do sound as complicated as possible. They conflate complexity with quality. For anyone other than the photographer, the process is irrelevant. It is the results that count. As Dan Burkholder once said, you don't get extra credit for it being hard. And work ethic without talent will only take you so far.