It was the proto-RTS game. It had lots of faults but it pointed the way to more refined games. Certain ideas, like building the harvesters to collect spice so you could pay for buildings and units, were essential to the successor games like Warcraft.
The graphics were shockingly primitive by today's standards, but they were fine at the time. Your mind did indeed fill in the gaps left by the minimal graphics, especially since much of the game was spent staring at dots on the mini map.
Later on, there was a lot of experimentation in RTS games with what kind of buildings to put on the map, like walls around your base (or just about anywhere else), what constituted victory, command and interface, and so on.
The slick presentation and easy interfaces we now enjoy were achieved with an enormous amount of trial and error. Back then, nobody could know where computers and video games would go, and the current devices and interfaces we take for granted could have gone in a completely different direction. Anything was possible.