Before cPanel, I couldn't tell you what I used on shared hosting back in the 2000s...
I used cPanel before finding Plesk as a cheaper alternative. Between the two, I still operated CentminMod (CMM) as a "control panel" of sorts (there is a "panel" of options of sorts, but most of it is CLI).
Prior to the owners of cPanel buying Plesk, you could host up to 3 domains on 1 instance for free. So, I could spin up cheap instances and host small sites, cutting some costs.
However, Plesk is now, I believe $21, but unlimited domains. I suppose I can't complain...
However, I've been looking into aaPanel (it's free, but there is a paid Pro option, monthly or like $800 for a lifetime license, with the latter I'd get if I want a true alternative).