I only started a few years after you did and early D&D was also a thinking person game. Highly lethal with XP for gold which rewarded avoiding combat.
The issue I have always had with SF campaigns is the limits of technology. The freedom of movement and access to information in SF is well beyond modern so it makes it much more difficult to make closed box puzzles. You tend to go into buildings, not ancient ruins and fantasy games have far more rules/materials to randomly generate adventure seeds and random encounters.
There is a lot of burden on the GM for a SF sandbox game than a fantasy one and hard to not have a sandbox, especially if trading between star systems is happening.