One of my favorite aspects of D&D is that is (rightfully) considered by many role-players as a lingua franca, a common language we can all use to communicate with each other, despite being more fluent in other languages (i.e., our particular favorite games). Whether your favorite RPG is Heroquest, GURPS, Fiasco or something else, chances are you have played or read some version of D&D. Even the people who don't play RPGs are often familiar with concepts popularized by D&D, such as levels and hit points, due to videogames and pop culture - and they may even think D&D as synonymous to RPG.
There are lots of people that see D&D as a mother tongue, of course. They have played D&D before other RPGs, and many haven't felt the need to learn new systems. But even amongst the ones who dislike D&D, its jargon is mostly common knowledge. Although this might have many different reasons, the fact that D&D was the first role-playing game around (which also gave it “naming rights” to lots of stuff it hasn't necessarily invented) and the most popular one during nearly all of the existence of the hobby (until today, if you count Pathfinder and other games that are heavily inspired by it) are certainly the main ones.
One of the interesting effects this brings is that almost every new concept you can think of has been tried in “D&D speak“ before. Wounds instead of hit points, character point versus rolling abilities on 3d6 and levelling up, percentages, dice pools, conflict resolution, levels of success, abstractions, playing with multiple characters, etc ad nauseam. All of this has been tested and discussed in the framework of D&D, since the very early days of our hobby.
It is quite difficult learning about a subject if you don't know the particular lingua franca. Even if you dislike D&D, I think you should learn about it if you have any interest in roleplaying games at all, as it will help you to understand other games.
Let me give you an example. When I first read Apocalypse World, a game that has little to do with Dungeons & Dragons, I had a hard time understanding it fully. Although I was very interested in the new ideas it brought to the table, its language made them hard to grasp. But them I read Dungeon World, the adaptation of the Apocalypse World engine to the language of Dungeon and Dragons, and everything became a lot clearer.
By using the familiar language of abilities, spells and hit points, Dungeon World made Apocalypse World easier to understand. By displaying the very core of AW - its most important ideas - in the well-known surroundings of D&D, DW made it stand out - even for some people that have no interest in playing Dungeon World.
You can do this with lots of games. Take Fate Freeport Companion or GURPS Dungeon Fantasy as other examples of gateways to games some people might not “get” at first. This doesn't mean you have to like them, of course (although I personally think all the games mentioned in this post are quite awesome).
D&D is a lingua franca in less metaphorical senses, too. It has been translated in innumerable forms to many languages, for quite a long time, and you could probably have a vague understanding of a D&D character sheet written in a language you don't speak or - who knows - improving your languages skill by playing D&D with people who speak other languages. This happens with other RPGs too - by taking a quick look at the german RPG Degenesis Rebirth, I was able to grasp the basics of the system (or a small part of it...), even without having played other editions of the game, or speaking any German at all.
|I can't read any of it, but it certainly looks good!|
The trouble with this lingua franca is twofold. The first one is that you can get too comfortable knowing that you can speak a language thats is familiar to almost everyone in the hobby, so you don't need to learn other languages. The second one is that you use the lingua franca as a simplified language, learning the bare minimum to communicate with other people. In both cases, you might be losing the opportunity to have fun and acquire knowledge, even if you want to play anything besides what you are playing now.
To communicate within our hobby, knowing the lingua franca is essential, but having a good vocabulary and learning new languages are also very important.