In my admittedly few years of playing DF, I have tried my hand in most aspects of the game. I usually play mods that make the game more complex so I've tried things in game that aren't even in the base game. I think, that while I have some experience with a bit of everything the game has to offer, what keeps me from being a master is how shallow my experience in some areas is. I have yet to successfully repel an invading army (but I have repelled ambushes); my exploration into the caverns are usually short lived and I have yet to encounter a forgotten beast; I have yet to create any traps more complex than the basic (constructed) stuff; my use of machinery is ironically primitive and rare since I never found much need or opportunity to do anything complex with them; I never had a fortress last long enough for my civ's leader to try and move in (though that is more due to my tendency to abandon forts at a whim, making them short lived); and quite frankly I could never handle fortresses with populations that go above a few dozen citizens (leading to the aforementioned short-lived forts). Also, yeah, while I did try messing with mine carts and tracks, I didn't get all that in depth with them.
I'm fairly experienced with most everything else (that happens in-game), but those aspects of the game are just too difficult for me to approach in a normal run with a fortress or I have little experience with because they are not things that I can mess with early on which keeps me from being able to better understand them.
Plus, outside of the game modes I'm also fairly inexperienced. Modding the game and messing with world-gen settings are things that I have done a bit of before, but nothing too in-depth.