I have made exactly four sets of airplane trips in my adult life: that is, four trips somewhere and four trips back. Across that decade, several things have changed, and maybe they're more noticeable to an Infrequent Traveller.
Strangely enough, I think airport lineups are getting better. Maybe it was a fluke, but it seemed to me that even the dreaded security and customs lines at Pearson (Toronto) moved quicker and smoother than they did in the past. Is it because passengers are now so familiar with taking shoes off and showing liquids, that things flow better? Or are the agents just moving them through better?
Where I did notice a hangup, more than once, was with the greater number of people bringing carry-on bags, some of those possibly over the size limit, aboard relatively small airplanes. These planes have three seats on the left and two seats on the right, and the overhead compartments are correspondingly deeper on the left. Passengers were having a terrible time finding places for their bags, especially on the smaller side. The airline is obviously aware of this problem, because they were asking for volunteers to check their bags (for free). On the return trip, I took them up on it, because I had a connecting flight with little extra time, and I was happy to have one less thing to trundle through the airport and fight for space with on the plane. (And my carry-on did get to Toronto with no problems.)
Airport food is horrendously expensive, even at the grab-and-go booths. Sometimes you are just stuck with it, so be prepared. But even short flights usually offer free drinks and snacks, so it's not worth paying for airport coffee or pop or bottled water if you're boarding soon anyway. I did buy a sandwich during one stopover, and a fruit salad while running through the Atlanta airport, see above.
It is definitely an advantage these days to have a computer, phone, or other device to keep you current on check-ins and changes. It's also a good idea to have a plan for accessing airport Wifi, if (like me) your life doesn't run with a phone. I put a shortcut to a site called Boingo on my home screen, which helps access public Wifi that doesn't just pop up automatically.
The biggest change, I think, was not in the physical or digital navigation of things but in my own perceptions, and the fact that (even being very Infrequent) I don't get mixed up as much anymore. The first time I ever came back through Toronto, I got hopelessly lost trying to find the shuttle van home. Turned out I was on the wrong floor of the terminal. Now I'm not even sure how I could have done that, because the van counter isn't that hard to find. But I was the kid who got lost coming back from the bathroom on the first day of school, so anything's possible. Moral of the story here: you're not stupid if you get mixed up in a new place; and after two or three times, you are going to feel, if not exactly at home, at least a little more in control.