Nobody, literally nobody, expects the game to be perfectly true to life, but the game itself is marketed as a realistic zoo simulator. It should strive to be realistic as possible within reason. The people, like me, who are always asking for the ability to make things more realistic are usually the ones who know a lot about zoos - the YouTubers don't, and aren't a good measure of what the game should be like.
"It's just a game" has never, not once, been a good argument for anything discussed in this forum. It's never been "just a game", and that isn't just me waxing poetic about it; that's how it's marketed. Simulation games are supposed to be as realistic as possible - that is their whole appeal.
In this very thread Chante all but confirmed that it was to do with animal welfare. The "technical limitations" mentioned appear to only be some minor clipping, as Rudi discovered, and that only happened in extremely shallow water, not the 2m limit most of us want it reduced to.
At times I wonder if Frontier should have called the game Planet Zoo Tycoon, (only joking of course) since it would seem, there are a few players confused as far as the whole concept of zoo simulation being modeled after zoos. I think there is a general disconnect from a small segment of the players, however, overall I have definitely seen a lot of progress within the community, and their enthusiasm for real life zoos and how they translate into the game. Some of the players and YouTubers have actually visited zoos and started to learn about them because of this game, so for me, that is a plus. But I definitely agree with you that if a player is making his assumptions based on YouTubers, instead of real life zoos, then it can end up like the blind leading the blind.
The one thing that I still do not understand is why would anyone have anything against a feature improvement, that allows for more flexibility within the game without affecting their current preferences. Adding a 2m limit does not take away the ability for players to create a 4m or even 8m tank, so I really do not understand what the issue is. This amazing game is all about creativity and flexibility, and the less restrictive it is, the greater the possibilities. Sure, we can still build realistic zoo exhibits, and just opt out of the new gameplay features and mechanics, but where is the fun in that?