Be the spawner and you won't miss out.
If you're not the spawner, then you shouldn't be complaining about hunt sharing. You wouldn't get to participate if it weren't for the fact others were trying to share the information with you.
Also, the Hunt isn't designed to accommodate world hopping because world hopping didn't exist when it was created. They haven't changed it to accommodate world hopping because they don't want players world hopping for hunts. They want players to be doing the hunts on the worlds they are currently playing on. Those mount achievements are intended to be done over the length of an expansion by those who use hunts as their primary end game.
If you want to world hop to speed up how quickly you complete the achievement, accept that you do so at the risk of not getting there in time.
Players are right there because they're the ones that spawned it, were already in the zone when it spawned or share linkshells with those who did. Contrary to popular belief, there is open world content and there are players who do that content. There have been numerous occasions I've been in a zone when something was spawned even though I was there for other reasons.
If you're relying on linkshells and show up after it dies, you're in bad linkshells. See if you can get into better ones. If you're using the Discord mobile app, make certain you aren't on a power saver mode that delays notifications.
People way overestimate how long it takes to get to a S rank. Most can be reached within one minute. The longest it will take is 3 minutes. How do I know? I've timed how long it takes to fly to the most awkward spawn points from the nearest teleport.
It's hard to be sympathetic to those who complain that they arrived to a kill one minute late when some of us have already spent an hour or more in the zone trying to get the S rank to spawn in the first place and we're going to have to repeat it for the next spawn.
They don't intend for every player to get the hunt achievements. They intend those who are willing to put in the effort over time (as in months/years, not days/weeks) to get them.
You don't have to spawn everything yourself. Spawners share information with each other about what they're trying to spawn so people aren't duplicating efforts or to team up to make some spawns easier.
I think they're fine with the S ranks, other than players thinking they should be able to get to every one on every world.
What they don't like are the Rank A trains.
You're talking about turning one of the few pieces of content in the game that truly feels massively multiplayer into single player or co-op.
Thank you but no. There's plenty of other content that can be done solo or with a couple of friends, including the hunt bills and even rank As from older expansions that tend to get ignored.