I don't think it's even been played since Richie's departure, but I may be wrong here since there was still the occasional odd performance of a rare tune in Europe 2013...

The touring page you're advertising for in your signature has pretty detailed statistics about each tour :D
The last time Just Older got played was in Barcelona, Spain on July 27, 2011.

While it is not one of my absolute favs, I like Just Older. Lost Highway is... well it's not great at all. It's better than stuff like The More Things Change, but I'd much rather have Just Older.

By the way, I feel like The Circle is when they really started releasing the "radio pop rock stuff" as actual singles. Stuff like Just Older might have been just that, but it was not a single. But What Do You Got? was one. Born To Follow was one. Saturday Night Gave Me... was one (written during the TC timeframe, and it shows). Although I guess Someday I'll Be Saturday Night also has a pretty adult contemporary Bryan Adams-ish soft rock sound to it. Still, curious thing. Misunderstood too, but that wasn't the first single.

That's more so what I mean. I'm not saying the second verse is the reason it's not been played since but I think that has more to do with it than Lost Highway taking its place.

What I mean is that before, Just Older almost always was played in each show, until arrive Lost Highway.

In the last 10 years, Just Older has been played with drops, and is no longer a basic song of the setlists.

Maybe it had to happen, but damn it, this one was so great at shows... and before was basic on the setlists.

To get some figures around here:
Bounce Tour: 83 Shows / 72 times played - number of different songs played (incl. covers): 61
Have A Nice Day Tour: 88 / 47 - 73
Lost Highway Tour: 99 / 34 - 100
The Circle Tour: 83 / 5 - 95
Live 2011: 59 / 9 - 102
Because We Can Tour: 103 / 0 - 90

I think it's a mix of different reasons.
First of all the number of albums to pick the songs for the setlist raised each tour (of course).
With the Lost Highway tour the band started to vary the setlists much more than the tours before.
And I also think that it's a vocal issue as well. Just listen to the early versions and compare it to the latest versions. Jon struggles with the chorus and uses a different kind of emphasis to make it through the chorus.
On the studio and early live versions he sings the way it's supposed to be: "It's noooooot ooooold" with the long note on the "not" and a slightly longer note on the old.
On later version he sang "It's not ooold" with only a slightly longer note on the old so that he had more breathe for "just ooooooldeeeerrr". And later on even left out the "just" and only sang "oooldeeeer".
So I think that might be one of the main reasons to get rid of it more and more.
I don't think it has something to do with Richie. There'd be a whole lot of other songs he wouldn't play for that reason either (Blood On Blood, Whole Lot Of Leavin', I'll Be There For You [ok, at least a hit]...).

Damn! A lot of great points I didn't consider. Thinking of Just Older as a song harder for him to sing really is something else but I think you're right.

Trust me, it's not an easy song to sing. The chorus is not THAT high, but it still was somewhat above Jon's post-2003 comfort zone in range and would probably be almost impossible for him to sing nowadays.