The other day I wrote about rules weight and player buy-in.
A few more thoughts.
Rules weight isn't purely determined by how well you know them.
It's a strong factor, though. A simple-ish game with rules you don't know well will play slow and require rules lookups and run clumsily. A complex game you know by heart will play as fast as the game can and run smoothly. The latter will always run more slowly than the former, assuming equal rules knowledge.
You need player buy in for complex rules.
Just as a practical matter, if you use complex rules or ones with large decision trees (say, full-on GURPS tactical combat), players need to learn some of them. Even if they can just use plain language to explain what they want to do, someone needs to turn that into in-game decisions.
If you don't get sufficient buy-in, the game will grind to a slow crawl. There will be slowdowns for sure, possibly arguments, lots of "I didn't know you could do that!" and even more "it doesn't work like that" even when it does because of half-understand rules derived from past examples.
Someone has to know the rules. It helps if someone equals everyone.
As much as I don't really mind "just tell me what to roll," it's offloading rules knowledge onto others. And if you want to do complex things, or have choice be up to you, it doesn't work as well.
In other words, if you're just saying, "I chop that guy with my sword! I rolled a 13, what happens?" then "just tell me what to roll" works well enough. Once you go to "I want to chop that guy with my sword. What should I aim for? Should I step back after? Can I pivot after to face this guy? What, is there a tricky way to get better odds? What are my chances of hitting?" etc. then you're just making other people do the nitty-gritty of knowing the rules. They need to present your options like a menu so you can choose.
A corollary to this would be that you probably shouldn't complain as a player when you suffer for not knowing things you choose not to spend time learning. After all, you're putting it on someone else to know it for you.
Know your group.
If your group has lots of people willing to put in time learning the rules, you can add more rules with less consequence. If your group does not, or has players whose PCs will directly be impacted by those rules but who do not like to learn rules, it's probably going to have negative consequences. Know if your group does better with more rules layered on top. Even a very good rules addition is a negative if sufficient players don't understand it (or want to!)
So, anyway, I think my idea is this:
- rules complexity is a factor in rules weight.
- player buy-in is required to make rules weight light enough to play well.
- lack of player rules knowledge is more of a problem the more rules you use and options within those rules.
All of this probably comes off as a little rant-y, which isn't my intention. It's just a thought about how to choose how many rules and how much complexity you want. It's got to reflect the investment the players put back into the game.