If in your opinion realistic = barely color then that would be applicable, but tinting or desaturating the entire screen is nothing but a very tiny adjustement.
To make a realistic look from a vibrant style base you have to change textures individually - not wholesale. After all, a bright red star is not less bright red in a "realistic" looking world. Man made objects however would be very different in "realistic" and extremely vibrant visual style. Colors could possibly be slightly more muted, but most importantly they would have to be much more detailed in surface detail, colors would be more tuned to each other (so no rainbow ship, but only very few select colors per object) and also possibly usage of much less fully colored hull panels. Look at the newest Bladerunner movie. There is color everywhere... yet it is not looking vibrant at all.
Not only is it about colors and detail on objects, you would have to change effects and such as well. Having some option for visual style is pretty much out of question. Just like you can't just slap a cell shading effect on a realistic looking game and expect it to look good as a comic-style. It just looks half-arsed.
Older X titles were photorealistic and grown up, huh.... lets take a look at the pirate ships in X2
Those are extremely cheesy ... X2 is extremely basic in it's look. To try and put that on a modern game would look terrible to most people i bet. If you consider current style Lego-like, it would be like Duplo-esque instead.
X3 on the other hand was very different from that. X3 was much less chunky than X2. The character displays didnt quite match that style but i liked it a lot more.
Trying to make simplified 3D visual style look good (say X2 in modern times) is very very difficult. It is much easier with 2D games. Most 'artsy' 3D games with simplified look use either some key element (neon glow) or hand-drawn textures - which is pretty timeconsuming compared to modern pipelines. Just reducing texture complexity and object detail does not work, it just makes the game look old.
The radical change in style from X2 to X3 was justifiable, because of the progress of technology and techniques. The same does not apply for X3 to XR and X4. They just change it because they feel like it. Which would is their right, but it completely waters down the feeling that these games are in some way connected.
With the changes in background due to gameplay (e.g. JD elimination) this feeling is reinforced even stronger. And this was my biggest gripe with ES decisions for XR and apparently looks like they are repeating it for X4 . It's like playing a completely disconnected game every time, with the exception of the name and stories in background that are borrowed from each other.
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Highways:
I dont hate them, but the primary reason i dont like them is, that you have to be ON the highway to interact with the main traffic in any meaningfull way. And there is no way to observe trade routes in person, because everything is too fast to be identified.
In X3 you see a trader in sector and can tell the destination. Now you can deduct what the trader is propably doing, what cargo he has, how long it takes to get there. You can then send something to investigate the station and possibly cut the trader (buy something off from his nose). With highways thats only possible if you have a gigantic array of scanners/sattelites. In X3 you could do it in person.