My username may give away what I do for a living ?. I am usually loathe to comment on such matters as it would not be looked upon as very professional. However, what you would be suggesting would be "ideal for some"... but, I'm afraid, simply not workable in real life. As you can imagine, aviation and holiday companies are really struggling to hold it all together at the moment in a very challenging environment. Commercially, this far fetched idea is totally unworkable for several reasons. We have watched the sad demise of Monarch, Thomas Cook and FlyBe most recently, with probably more to come. The grounding of the Boeing 737 Max, which still isn't back in operation nearly a year down the line, Volcanic ash clouds a few years ago, sand storms, terrorism (remember Tunisia and Sharm el Sheikh), & now a possible world pandemic to contend with, is taking its inevitable toll on the holiday industry and aviation. There is no way that a whole plane could be designated just for adults only. That would mean a whole plane would also have to be designated for those with children and infants of various ages. Children on our aircraft are considered to be adults at 12 years of age and are deemed able to open an emergency exit. So, theoretically a 12 year old would be able to travel on a separate aircraft from his/her family with younger siblings, which simply would not happen. Similarly, on the designated aircraft carrying just the young families, from a safety angle it would be a total nightmare. There are so many restricted seats where children are simply not allowed to sit due to strict regulations. So.... airlines would not be able to sell any of those seats to families at all, as they will quite rightly not want or expect to be separated. Neither should they. Those seats would remain totally empty. So....who will occupy them to comply with safety regulations? It will mean that the emergency exits would be totally "unmanned " and that is against regulations, so the aircraft wouldn't ever leave the ground! We simply would not have enough aircraft available to segregate.
Bear in mind, young children's ears are often very painful when flying as their tubes are narrow and undeveloped. A lot of the screaming on board is due to this fact and a degree of empathy is needed, as "most" parents are beside themselves with worry when this happens. Yes, you can get very unruly families where naughty children go unchecked. Yes, of course it's much worse in a confined space, (try pouring hot water successfully when a toddler is let loose in the cabin under your feet!).
Commercially and for safety reasons, this simply isn't going to happen. Even if it did, where would you then draw the line? As someone has said...a whole plane load of stag and hen parties? (Safety again?!!) A whole plane load of people with reduced mobility issues? It simply isn't going to happen if you are travelling on a holiday airline. Holidays are for everyone. Hotels are a different matter, as many of the safety considerations will not apply on the ground.
Sorry, but apart from earplugs, I'm afraid there will be no significant changes! Believe me I empathise after a 15 hour day in the skies in the summer...(at least you can get off the other end!) Lol.