Train represents a potential for the same travel but usually looks worse in contrast to flying in terms of money and time.
So unless taking the train is the point in and of itself (as in my Vienna to Venice adventure) it's seldom worth it. So yes I don't think I want to fly less.
The one exception to that is with little kids. NYC to Cleveland is a sub-hour flight or a 7 hour drive. As a single guy I flew. Now I drive at night so the wife and kids can sleep through it. Maybe that's a bit analogous to the night train though it's also very cheap.
As a customer, that is more or less valuable to you depending on how much you worry about the impact of planes on the environment. I am self identifying as someone for whom that isn't one of the decision criteria. If that was my number one concern then I wouldn't fly. But then I guess I wouldn't travel via any mode.
From the restfulness point of view, not so much. I am not a light sleeper but the train was noisy and jerky and the bed narrow with your body perpendicular to the direction of travel so it kinda sucked. Not really a "hotel on wheels" from that point of view.
There was no security to deal with, however on the train from Budapest to Vienna that I took the day prior was searched by armed police. Perhaps Vienna to Venice is a lesser destination for people the authorities want to screen out.
I don't have climate anxiety and I fly around a ton. On a 3-week euro tour where money wasn't really an object, it's totally worth it for the experience to do the night train. If time or money mattered then this would not have been the way I'd go.
As an aside, I've seen the train at best "break even" on time and experience. The Acella between Boston and NYC, and the Eurostar between Paris and London take longer than flying, even when factoring in the travel to the airport. If you want the uninterrupted train time to read or snooze then maybe it comes out ahead. Price wise the train is way less practical but with the company paying for my travel that's not an issue.
As Americans it's customary for us to genuflect to Europe for it's enlightened train connectivity and there are places where that works very well (eg Paris to Stroudsburg) but for cross-country travel it's not really that great.