Since some times (long time actually) I faced numerous lags during games preparation :
Lobbies listing refresh and sort (horde and escape)
Entering a lobby
Personalization (class and skins)
Ghost countdown before game
It made entering the game a pain. But I thought it was « standard » and as my network was not the root cause I let it like that until this we.
I decided to uninstall the game from my XBoxOne S and reinstall it again.
And miracle : no more lag, refreshing is almost instantaneous and personalization inside a public lobby is fine again. No more ghost countdown.
Installing the complete game with DLC took me nearly 12h but it was worthy.