Hello; A few years ago I responded on another forum much as you have in your post. It was early into my use of online tropical fish forums. I was not at that time aware of the dogma concerning some fish keeping practices that had developed when I was not looking. At first I thought that if I wrote about my point of view in a clear and concise way they would be able to follow my point. In the end it did not matter. Some of my posts were edited when I talked about my experiences and opinions that were outside the bounds of their dogma. I eventually quit using that forum.
While many on this forum have disagreed with my points of view about various topics, I have been able to express myself more freely. In fact, some of the long back and forths in these threads have allowed me to pick up new information and insights about the hobby. I find it a positive that the moderators will allow discussions about touchy topics.
Back to your point. While I too have ideas about what is a proper tank size for various fish, I have found myself housing a fish in a tank not ideal. It happens. Starting from the notion that few fish keepers can have the sized tanks that approach a natural setting, we therefore have a compromised setup from the get go. Even a modest natural setting will likely have hundreds to many thousands times the volume of a tank. We make up the difference with regular water changes and to a lesser degree the filtration. As you say it is work, extra work to house a fish in a tank smaller than ideal. It can be done.
I have known people who try to keep Oscars in 55 to 75 gallon tanks. One in particular never accepted the idea of needing to do more than have a big filter going. No regular water changes and no gravel vac. Needless to say the Oscars did not survive too long. The Oscars are gone and the tank is sitting empty. He stopped by my home and liked my tanks. He called one evening talking about setting up his tank again. He asked if he could simply add water to the tank with the same, not yet cleaned, gravel and go. I went thru all the things he needed to do with the first being to scoop out all the gravel and spend a few hours rinsing it. Thank goodness that, so far at least, he has not done anything with the tank. I do not intend to encourage him to ever have fish again. On my scale someone keeping an Oscar in a 75 and is willing to do the extra diligence about the water is a much better situation. Do I ramble?