Complexity isn’t what I’m looking for, it’s options. While option-rich systems can be complex, it doesn’t necessarily have to be.
Part of the problem is that we don't really have a good
single word for "rich" systems as opposed to merely overwrought ones.
Because that's usually what people are asking for when they say complexity. They don't want a needlessly overwrought, janky mess that requires constant maintenance just to function. They want something that involves "deep" choices. Thing is, most people are aware that making a simple set of rules that lead to "deep" or "rich" choices is really,
really hard. Go is famous for having extremely deep strategy despite having few rules, but it's famous for that specifically because it's
hard to pull that off.
So, in general, if a ruleset is simple it usually isn't deep. People thus ask for a "complex" ruleset, because they presume that it will be a
well-made complex ruleset and thus not needlessly overwrought or janky. It would be nice if we had a word in English that meant "complex enough to offer a deep/rich play experience, but not enough to be unwieldy or overwrought," but we don't. So people use the ready-to-hand word.
Bit like how, in casual conversation, we have a single word that means both "having healthy self-regard" and "having excessive and unhealthy self-regard," but we still constantly use both terms: both "pride parades" and "pride goeth before a fall." Not much interest in renaming them to "<group> Healthy Self-Worth Parades."