One thing I’m liking about the Five Moons system is because there’s no limit to the number of cronks/spells/stunts you can learn, I can create really specialized, situational abilities that don’t have much use outside of those circumstances, but characters aren’t penalized for learning them.
For example, let’s say there’s a dark forest where giant spiders are a common monster. The local people probably have developed special combat techniques and spells for fighting giant spiders. If you go there, you can learn them. After you leave that forest, you might not ever need those techniques again (and you probably wouldn’t ready them as part of your morning routine unless you knew you were going to fight giant spiders), but you still have the option to quickly ready them (by leaving an open slot) if you need them in an emergency.
Compare this to what we sometimes called “the sorcerer problem” in 3E/PF, where a sorcerer learns a very limited number of spells in their adventuring career. Because of that limit, you wouldn’t want to “waste” one of your precious spells known on an obscure spell that has limited utility. For example, unless you knew that giant spiders were going to be a common enemy for most of the campaign, you’d never take a Sammy’s Spider-Blasting Spell when you could take Adam’s Anything-Blasting Spell… even if SSBS spell does x2 damage compared to the AABS.
(Conversely, spells that have multiple effects become no-brainers for sorcerers because it’s like you’ve learned two or more spells for just one spell known… which is why 3.5/PF split a lot of them into multiple spells.)
The same thing happened with fighters in 3E/PF because they have a limited number of bonus combat feats; if your primary weapon is a longsword, you’re better off taking another feat that makes your longsword attacks better instead of picking up a shortbow feat on the off chance you have to use your bow. And you almost certainly wouldn’t take a “+4 to weapon damage against spiders” feat unless you knew you’d be fighting spiders all the time, because a “+2 to weapon damage with your longsword” has more utility.
This also means I can have unusual abilities in the game that don’t have a lot of combat utility, but add a lot of flavor to the campaign world, and the players can learn them without worrying about “wasting” a limited resource. For example, there could be a curse that makes the target smell like rotting garbage, or a fertility spell, or a charm that calls cute little forest animals to follow you around all day, or an exercise routine that gets rid of a hangover.
More options, more fun.