I'm not sure if you're joking or not, but the behavior of journald is fairly dynamic and can be configured to an obnoxious degree, including compression and sealing.
SystemMaxUse= and RuntimeMaxUse= control how much disk space the journal may use up at most. SystemKeepFree= and RuntimeKeepFree= control how much disk space systemd-journald shall leave free for other uses. systemd-journald will respect both limits and use the smaller of the two values.
The first pair defaults to 10% and the second to 15% of the size of the respective file system, but each value is capped to 4G.
If anything I tend to have the opposite problem: whoops I forgot to set up logrotate for this log file I set up 6 months ago and now my disk is completely full. Never happens for stuff that goes to journald.
Yeah, and you need systemd to read the binary logs. Though I think there may be a setting to change to text logs, I am not sure because I avoid systemd when I can