I think this is one of the biggest things driving me nuts, especially with many of my friends returning to the game in prep for Evercold or trying out the game for the first time.
I've played on Balmung since 3.3 when I joined the game, but for years now other than a single hotfix patch that it opened, it has remained congested/closed to transfers and new players. But that means I am punished for staying on the server I started on because my friends can never play with me there. I can never make them a tenant on my house, I cant mail them cool stuff/surprises, we cannot form an FC together, we cannot do Firmarment or Cosmic Exploration together, ect. So my only option is to give up the server that has been my home for 10 years now, abandon my house I've had since Stormblood, and start fresh on their server (knowing I will never get to revisit Balmung because it is eternally congested), or just give up on all that stuff.
And as noted in this thread this problem has only gotten worse in 7.4/7.5 as now all of Aether, all of Crystal, and some of Primal are now congested and closed to new characters as CB3 keeps trying to push more players to Dynamis, which Creative Business Unit 3 seems to fail to understand that new players with friends in the game already want to play and hang out with said friends, and said friends are not likely to give up their houses, friends, and homeworld to go play on a dead datacenter.
