my NetworkManager-wait-online.service was also taking about 8 seconds on my laptop
i ‘masked’ the service to stop it coming back, and now boot times are much quicker
angelo@thinkpad 20:09 ~ $ systemd-analyze Startup finished in 1.670s (kernel) + 3.096s (userspace) = 4.767s
angelo@thinkpad 20:09 ~ $ systemd-analyze blame 1.927s networking.service 1.636s plymouth-read-write.service 1.108s systemd-backlight@backlight:intel_backlight.service 867ms apt-daily.service 464ms dev-sda1.device 418ms nmbd.service 361ms samba-ad-dc.service 309ms gpu-manager.service 228ms smbd.service 196ms accounts-daemon.service 180ms systemd-logind.service <snip>
no ill-effects noticed so far crosses fingers 