Oh yeah, this has totally happened to us in the last 2 years.
DD, now 19, loves DIsney, but just became nearly intolerable to be around, do anything with. That was at home as well though, She's finally come around.
DS, 16, could totally leave Disney behind, if there were other options. He'll go with us, but he's pretty much only interested in a few thrill rides a day, then he goes back to the room, and watches TV, movies, or plays Switch, etc. He's not very social, and really needs that downtime, out of the crowds, just relaxing.
Both want other destinations, but we also own DVC, and it's familiar and easy to go to Orlando. But we KNOW we need to branch out eventually.....
Solution for us: IF they go to Disney with us, we totally agree to doing our own things, and splitting up. Sometimes that overlaps, like for rides like GotG, but sometimes not. THey have money, their phones, etc, and we just do what we want.
I do totally get being sad about it. We've had so many happy times, happy memories of Disney trips, from toddlers to young adulthood, and it's sad to realize those kiddie days are gone. But just have to find a new happiness. .
I"m about to take a spring break trip. DH went on a solo trip in Jan, so he's probably not going. It was going to be just DS and me, and he is making sure the Roku stick is packed. All of a sudden, this week, DD decided to join us....hoping we all have a great time.
We do also do Univeral trips, either on its own, or now add a few days to the DIsney trip. Have 3 days there for spring break. We all love the thrill rides there, HHN, etc.and kids have a lot more to ride. SeaWorld for coasters was great too.
Good luck planning.