It is not about login.
SSA is a turn based game where the netcode should not even be a issue but...
Some times you can't change your party (you have 30 seconds but it ignore it thinking you dropped the connection), the servers doesn't receive the commands, you drop in the middle of the battle (some automatically lose other you enter in auto mode that fuck everything), a lot of time mechanics doesn't work, etc.
It can be server traffics? Yes but that is part of the netcode lol you need to put more servers... I don't know... the game is still very very popular.
Ohhh and bugs... there is maintenance every Wed but it always have some new bug and old bugs are never fixed.
To you have an ideia parts of the story translation become Chinese after maintenance and are never fixed.
They support are really poor.
Eg. Athena (BTW this one is fixed now).
But it is Saint Seyia... so we continue to play due the nostalgia.