System First Design (A Titterpig Helper)

 Plenty, arguably the majority, of TTRPGs are focused primarily on narrative or purportedly providing storytelling tools. Along the way this emphasis has driven a noticeable wedge in the hobbyspace with a tendency to uphold, exonerate even, the concept of "roleplaying" and left the game portion languishing. Usually dismissed.

 I'm set on pushing back against this. I hope you will join me.

Groundwork? Yeah! I Sure Hope It Does!

 Let's not get caught up in defining "system" in this particular case. The name is ultimately catchy shorthand. I'm not trying to erase the concept of narrative either. Let's experiment, try a different approach, and at worse learn some interesting lessons. Cool? Cool.

 As a baseline this design philosophy is about taking the game components or "play pieces" and examining how they feel / what they do when engaged on their lonesome, then building a game off that starting point. In terms of a game component or play piece the first and obvious example is dice but I would in this stripping down also implore a removal of said assumption. Explore cards, marbles, dominoes, coins, tops, maybe even paper itself. The usage of a wooden block tower in the game Dread (and other, similar RPGs) is a decent example! Pulls from an increasingly unstable tower creates tension wholly by itself and doomed horror matches up easily.
 One could contemplate it even further: How does it feel constructing the initial tower? Is the collapse inherently negative? What about the moment between extracting a block and placing it on top? etc.

 Secondly, and by extension equally as integral, designing your game with these materials themselves being where play begins and/or repeatedly returns, acting as the driving force behind roleplaying.
 EX: Dealing out a hand of cards and placing said cards down (perhaps in designated spaces) for corresponding actions/effects. Citizen Sleeper accomplishes something similar with dice, so I've heard!

 This might even result in removing character creation as we typically expect, opting more for discovery as you go. Certainly Lifepaths from Traveller, randomized attributes/features in a game like Cairn, or Oracle Tables in various Solo-RPGs are not far off from another method which more closely embody this. I bet you could go deeper however.
 Or is there even a need for consistent characters in this at all? Certainly collaborative worldbuilding games alone challenge that notion so maybe this should too.

 And finally, less design tenant and more consequence I encourage embracing: Games become more tightly focused. If the rules don't cover it? You don't do it. Or, at least, you are not concerned deeply about it, highlighting it, adapting rulings on the fly for it…
 There might be an instinct to see this as a gap in need of filling by creating "generic" options folks can fall back on or, to give permission for disregarding said ruleset in favour of "roleplaying."

 It doesn't detract from roleplaying! Instead these bits become linked. Playing the game is playing the role.. when the mechanics and their deployment are emphasizing corresponding sensations. And that's what you'll have made!
 You don't go to a hockey rink to play baseball.

Throw Your Own Titterpig Potluck

 Considerably preceding Mechanized Make-Believe I've had this exact concept sorta stuck in my mind. I return to it regularly and never feel it becomes less relevant, less intriguing. What finally got me blogging was putting in practice, for a couple of (at time of writing) unpublished game projects, this conceit. So I'm including below a sort of.. Game? Procedure? Something you might find useful in accomplishing the above. Worst case: You do a fun thing with some friends.

Titterpig Potluck

1.  You and maximum 2 other designers select a game component
2.  Explore and record what using said component evokes
3.  Bring your findings together and build out a game inclusive thereof
4.  Layer in fictional elements you find collectively befitting
5.  Try out this newfound TTRPG!

 Remember: Avoid or handwave fictional elements that are not directly stemming from the mechanics themselves. These rules cover the parts that matter. If something fictional doesn't loop back in, it is not important.
 Game first, Roleplay second.

Addendum: It cannot be stressed enough how none of this is a push for "simulationist" games.
Wargames are neat and all but no, this conclusion is completely off-base and you've significantly misread the entire post.
Please try again. I believe in you.