Wiki could use an entry for the 4X genre, but OTOH: «4X (abbreviation of Explore, Expand, Exploit, Exterminate)» applies to many RTS too, since most RTS have resource to exploit, fog of war, allow to build, and requires to exterminate opponent. (quoted text was taken from wikipedia).
But then, «The term "4X" originates from a 1993 preview of Master of Orion» so the canon game is turn based, and happens in space, I guess. Here one can link toward [the blog](
https://freegamer.blogspot.com/2020/04/ ... ee-4x.html) which last entry is about that kind of games.
I guess it's safer to stick to the "modern definition" according to wikipedia:
In modern-day usage, 4X games are different from other strategy games such as Command & Conquer by their greater complexity and scale, and their complex use of diplomacy.
Reviewers have also said that 4X games feature a range of diplomatic options, and that they are well known for their large detailed empires and complex gameplay. In particular, 4X games offer detailed control over an empire's economy, while other computer strategy games simplify this in favor of combat-focused gameplay.
Looking at FGD wiki for candidates (not named yet) that I remember a bit:
So, mindustry, widelands are clearly 4X games according to both 1st and modern definitions. Unknown horzons, maybe, I don't remember if there was a way to have soldiers or other aggressive means to remove opponents, but it definitely have the economics thing. Cultivation could also be a candidate, I think I remember the goal was to be last in line, but I don't remember much about the resource control.