It seems my problem was related to the Bluetooth module…
In fact my Bluetooth wasn’t working… Until now I didn’t care…
But I managed to solve that (explained here No Bluetooth settings available (having a dual WIFI/BT card) - #7 by sanjibukai) and this also solved my long delay…
Now systemd-analyze blame displays something like 6 seconds…
Edit: the exact fix for the delay in my case was to set bt_coex_active=Y in /etc/modprobe.d/iwlwifi.conf