Indeed, I'm using Debian on devices with less memory than that and it's still working with jessie and stretch (and thus systemd) with no memory issues.

Of course, not having a desktop environment doesn't necessarily mean that there are no memory-heavy processes running; it would be interesting to know what was running on that system.

I didn't notice any particular lagginess with stretch either, but then I'm not using Gnome, it may be that its last version is slower / heavyer than the previous ones. The rest of Debian is still unaffected, however.