When me and my flatmate redid the 2.1-2.4 storylines very recently on a pair of alts (currently working on early 2.5), we didn't have to wait long at all O.o At the most, two minutes or so. Admittedly, this is probably because my alt is a tank, so when we're paired up, she (as dps) is benefiting from that. When we did Levi, I think we had five people who watched the opening cutscene (in other words, who were most likely new).
Also, we're probably on a world with higher population, which helps as well.

There are also "prime time" hours for when the most people are online. This is usually around 6pm-midnight, server time. Too far outside of that, and you'll have fewer people doing stuff, because they've already done it, or because they're busy with school/work or other irl business.

I agree that it's slightly annoying to have to do everything 2.X before getting to 3.0, especially since some parts of those patches tend to be very... "non-essential". Nowhere near as much as the Drybone sequence was back at level 20, or the whole bit around 30-32 in Costa, but it can still be very overwhelming. But once you get to the end of it, around 2.4-2.55, you'll understand why they decided to make people go through the story.

(Though to be honest, it's been very interesting to go through the 2.x story after seeing bits of the 3.x story, because the things they talk about in some of those cutscenes... When I did them the first time, I had to wait for months between each patch, so some things I saw two years ago. I barely remembered half of it. Revisiting it in fairly short succession gave me a lot more appreciation for SE's story building.)