I think the devs already understand this, but smoke/steam is really unrealistic at this point. The color is off, at least the cylinder cock steam should be white, and the main smokestack should have darker smoke. Speaking of the cylinder cocks, they should only be opened the first moments after a locomotive starts from a complete stop, and the puffs should be synchronized with piston movement and the ‘chug’ of the locomotive, as should the main smokestack, it seems that it constantly emits a huge plume of smoke, even when the locomotive isn’t actually releasing steam (AKA, when it is stopped.) Overall, the steam/smoke lasts far too long, compare any real steam locomotive photo to one of the screenshots and that is definite, it also doesn’t puff up as much as real steam would. And, finally, there is no whistle steam.
Of course, as I said, I believe that the devs understand this, but I had to put all of this in since it doesn’t appear that the issue has been fully addressed in any of the recent screenshots (although one of the screenshots of the Class 218 features smoke, which already looks good, as far as I can tell.) Although smoke and steam don’t change gameplay directly, it is a detail that should be considered since you see so much of the stuff, so the more realistic it is, the better.