I Want Fewer RPG Systems
The cost of learning a new RPG system is...well just the cost of learning a system. Even for those who like the process, it takes time, and it limits those who can play the game. Ask a regular gaming group of four people to try 'FISHBLADE: The Diceless RPG', and chances are high that at least one will veto the suggestion.
The benefit is, of course, a bespoke system.
So when is the cost worth it? I can't put a number on it, but I can plainly see that the number of systems out there are not really worth the cost of learning the lot.
If only system designers felt more at liberty to use existing systems, and say this thing runs on system-X, then those designers might have a wider audience, and the audience would have more (realistic) choices.
The use of fewer systems becomes more obvious once we zoom in a little. Take Changeling: The Dreaming, for example. It's a White Wolf game modern day, high fantasy, and a big favourite of mine. Now let's ask what the ultimate system for this vision of the world - this setting - might have been, and note that the question never generally arises. Surely it could have been improved with some deviations from the standard World of Darkness ruleset. It would be bizarre if the best possible system for Werewolves fighting spirits and mutants, and the system for Vampires having political feuds, and the system for delusional kids grasping hopelessly at a shared fantasy, were all identical.
By having one system for Vampire, Werewolf, Changeling, et al., we have lost something, but we have lost something so small that nobody notices or comments on it. And we have gained the ability to pick up a new game - yet another fantastic White Wolf RPG - while only learning a couple of cantrips, rather than on-boarding players with a full new set of rules.
I don't think it's a coincidence that the OSR RPG scene has so many rulesets attempting to be compatible with old modules. It's not just about being able to play old A,D&D modules - it's about a promise that the rules will be easy to learn.
And, if I can zoom back out again a little, the RPG rulesets really are something else. Monopoly has a page of rules. Extremely German board games with 12 sets of pieces of plastic, and 3 different card decks have up to 8 pages of rules.
RPGs have a fucking book. D&D itself has three books which people consider 'core rules', and is not - even then - complete, as it requires an adventure to be complete.
As usual, I lay most of the blame on copyright. Perhaps systems cannot have copyright protection, but they are littered with enough 'trademarks' and 'um, actually's that people worry about using other rulesets in their games.