Honestly, I don't consider that handicapping yourself at all. The more you play the more you realize their is a large variety of styles that can and do win on any level.
I've always disagreed with this. There is absolutely no harm in ever picking your chosen leader on any level. Some people are quite spectacular players with 1 Leader - no one else. Just because someone else can win with random leaders doesn't make them a better player unless they win more frequently. If the person who only plays 1 leader has a better overall winning % on any given level, then they are the better bottom line player - assuming the random player cannot match their winning % if they use a single leader, which would be doubtful seeing how they have spread out their expertise.
Anyone can disagree with anything. There's some validity to your point - there are ins and outs of playing a civ or race where you can get a little better by focusing on them. This is not unique to civ - most top-of-the-line warcraft III players also use only 1 of the 4 races for example.
But, choosing one's own race doesn't necessarily mean you're not a "standard settings" player. Hell, I thought you *could* pick your own civ if you just click "play now".
But don't assume this "spread of expertise" is necessarily damning. I don't think, for example, that Unconquered Sun or ABigCivFan favor one civ or leader (or even a couple), and they're among the best players on the forum. Not everyone can do it, but some people have the talent to switch between leaders and styles and see the tradeoffs with less experience investment. For example, one of the warcraft III pros would switch between Undead and Orc. A lot of players like to argue that certain races match up better against others, and do doing that was advantageous. Whether that's true remains unclear, even today, but one thing that *is* certain is that some PLAYERS are weaker vs one or the other race, and this guy could play both equally well...either race on par with the best of the best in the world at that game.
The race variance in WC III is much greater than the trait/civ variance in Civ IV, but there are more nuances total due to the # of civs and traits. Still, it's not out of the question to learn the patterns. In fact, there's something to be said for playing random while learning at least at first, because it gives players the opportunity to 1) find the leader that's the best fit and 2) think critically on the advantages of their setup and how to use them in the context of the map.
Then there's always the factors like playing one civ becomes stale for some people and any benefit from doing it could be surpassed by the distraction of wanting to try new things. It's not a cut and dry "one civ, you'll be more effective" thing. That will vary from person to person.
As for what ISN'T standard settings, I'm talking about the more OBVIOUS things that cook a game and make a win on deity far more hollow:
1. Choosing soft leaders as OPPONENTS that allow you to manipulate your VC from the start of the game.
2. Picking map scripts where the AI is awful on purpose (do an islands start with 1 civ/island and high sea level for example ----> everyone gets a 6 city island or so, with minimal trades, and it's very easy to conquer people because they have poor production...this is obviously not the same as playing on fractal).
3. Playing "marathon" speed (it's been analyzed a lot - if a player intentionally manipulates marathon to its potential, it *is* easier...but this is more for other people, I know crusher realizes that marathon is easier already).
4. Removing tech brokering, turning tech trades off, etc
5. Permanent alliances (cmon...I can beat deity like >50% of the time using PAs, all you have to do is latch on to the #1 science or culture AIs and ride the storm).
6. No barbs
7. Exception to chosen civs: Inca + quecha rush.
That kind of stuff.