We were on Apex for Thanksgiving 2021, so the ship was still at less than half capacity, but there were definitely lots of families with kids. Probably not as many as on Royal, but they were there. Happily, almost all were very well-behaved.
I did want to specifically address your comment about The Retreat. I inferred that you thought that being in The Retreat would allow you to separate from families and kids. That was what we thought, but that was certainly not the case on our Thanksgiving cruise or March 2022 Edge cruise during Spring Break.
Even though the ships were well below capacity for both sailings, The Retreat was fully booked, probably due to Move Up bids. On both cruises, Luminae seemed to be bursting at the seams with multigenerational groups, and I suspect that this was a combination of families with kids booked in suites and grandparents in suites paying the upcharge to have non-suite guests join them for dinner.
Like you, I have nothing against kids, but am looking for a more adult vacation experience. Did it ruin my cruises to have kids in The Retreat areas with me? No way, but it just wasn’t what I expected.