Tradition would demand that to play a roleplaying game, you need some framework for people to use.
This is, I think, entirely reasonable - but there is a huge range of what this actually means in practice though - from seriously crunchy, dense rulesets, to those that focus on storytelling and narrative, to those that provide merely the lightest touch.
I am firmly in the camp of 'less in much, much more' when it comes to TTRPGs. Provide enough of a framework for people to actually play, and then leave them to it.
For the games I'm writing, my goal is for them to all have the same core system - SADS (named to both set the mood of all of them, and relating to the four core stats). On top of this, though, there should be a unique game and world - so the bones are familiar if people move between the games, but feel unique and flavourful.
There are some principles and rules I'll be trying to stick to when writing any rules:
1) All of the core rules should fit on 2 a4 (plaintext), or 2 a5 (laid out) pages. I prefer the term rules sparse to rules light, and this is the core of it.
2) Storytelling and narrative should be baked into the game. I don't want to write a generic roleplaying system - I'm not a talented enough rules writer - but have rules that help convey the tone of the game of the world it takes part in.
3) Death should be possible. Because of this, character creation has to be quick.
4) Leave space for players to explore the abilities of their characters, use their own creativity, and roleplay their character.
If I can stick to all of these, I will be happy.
Next time, I'll post one of the character classes from the first game - titled After the Burning. I'm currently choosing between the Enochian Judge, Fear, or Achorite.