There are several games that are not too complicated, that also has a charm, but necessarily, more complicated mechanism makes for more variable play.
The problem with complex rulesets is that they tend to make rounds very long which when you combine it with 4-6 players makes games drag for considerably longer than they need to be.
The worse games are the ones that try to mitigate that with multiple victory paths often partially RNG based or silly "sudden death" rounds after an arbitrary round count to force games to last no longer than 60-90min.
Sure you can point to games or systems like D20 but even then the core ruleset is fairly simple and uniform and the rest is just ad hoc that can be used rarely or not at all.
The one thing you need for a good board game is to have decent strategic depth with mechanics that induce interesting social dynamics, a lot of games try to implement the former by making it complicated by design and forget the latter.
For more modern games, Smallworld (https://boardgamegeek.com/boardgame/40692/small-world) is a great example for high replayability and relatively simple game mechanics.
The pinnacle of large rulesets is RPG games, anyway. With the possible exception of some 80s classics like squad leader and starfleet battles there are no rulebooks that compare in size to the foot or so linear shelf space of a full set of Pathfinder rulebooks.
Arguably Dominion has good replayability for similar reasons: you only play with a subset of the cards every game, and a lot of the strategy revolves around exploiting interactions between different cards. On the other hand Dominion is one of those games where there is very limited interaction between players, which perhaps doesn't make for great replayability.
I also play Hearthstone, the Blizzard card game, and that's a pretty awful example, sometimes, of bad randomization with all those effect that can range from harmful to do nothing to win the game on the spot.
The randomization in Smallworld is good because you always have a certain amount of control over it and you can plan for it/around it. On top of that the power swings are not really extreme (some race - attribute combos are stronger than others but the overall power range is reasonably small).
It is all about pacing an the impression of pace. In some regards it is like Cycling sprint discipline.
Watching top level Dominion games can be like watchig a different game. It has crazy, crazy depth and replayability.
I found Smallworld unfun.