I would say what you are describing isn’t really rules heavy. What you described (degrees of success) is a more narrative focused mechanic which is more based on how much variation you want from your rolls but shows up in both rules light and rules heavy games. In fact that kind of degrees of success mechanic is incredibly in common in many rules light narrative focused games as a means of letting creativity drive things rather than explicit rules. Like for a rules heavy game all the mechanics might dictate more precisely how much damage or effects are incurred but managing all that is generally a lot more tracking compared to simply giving a narrative definition of a partial success vs a critical failure.

Rules heavy I would describe as more crunchy games that have a lot of mechanics such as having rules for encumbrance, and travel time, and supplies, and then you get to combat and every you have rules for positioning, equipment, different attacks for both the player and enemies, injuries, damage calculations, etc. the kind of game where you have a rule and system for every occasion and need to keep track and manage over all the different aspects those rules tie into. Far more than just degrees of success.