So long as you're having fun, I suppose that's all that matters. Impressive that it's held your attention for all this time, too! How easy would it be for an absolute newbie to jump into the mix? Is the community friendly enough? Say I bought the game, would I be able to have fun, too, or would I be totally obliterated by the long-time players?
CS:GO is nicely divided up so that the really serious players tend to be separated from the beginners. They have different game modes to start: "Deathmatch", "Arms Race", "Demolition", "Casual" and "Competitive" (I might be forgetting one in there).
The most serious players are almost exclusively in "Competitive" matches. Teams are smaller, tactics matter more, and you have more control over who you play with. There are penalties for leaving the game, and you will definitely be abused if you are bringing your team down (and they aren't friends). It's no place for a beginner unless you're playing with friends.
However, Competitive is also matched based on rank so a beginner should be matched with mostly beginners too. They'll likely be better than you if you're just starting, but won't be too far out of your league either.
The other game modes are a mix of beginners and intermediates. You typically get a good distribution of newbies to decent players. For the most part, it's very friendly, but you do need to learn to lingo and understand the inside jokes.
For example, a common theme that crops up is "clutch or kick". "Clutch" means to basically come back against bad odds and win the match. Usually in a 1 vs. N scenario, but sometimes something like 2 vs. 2N or something. "Clutch or kick" means if you don't clutch you're going to get kicked. It's more common in Competitive when people are goofing around, but it carries back over to other game modes too.
A beginner has basically zero chance of clutching. It's just a form of trolling that mostly kids do. Though some might try to use it to pressure friends into performing better. Kicking is a voting system so there has to be enough people agreeing to kick for it to matter, and lots of people ignore it (after all, they're just as vulnerable). Of course, lots of people are sheep so sometimes this does happen. Sometimes it's fun too. It's just part of the culture that you get used to.
You will definitely be obliterated by the long-time players when you first start, but you can practice offline first to get a feel for it, and start out with the beginner friendly modes to get practice in before you set foot on a stage where your performance even remotely matters. Even still I have really really really bad days where I'm terrible. You get the odd troll harassing you, but you just mute them and go on with your day.
You can always play with friends too so that they can help you learn the netiquette rules and stick up for you. Not to mention, help you to improve faster. So certainly, it's a friendly community that anybody can join. It does have a steep learning curve, but if you consider yourself good at first person shooters then I'm sure you can learn to play CS.
It remains fun because it's skill based. You have to practice and develop strategies to succeed. Unlike computer opponents who are typically static and usually have weaknesses that you can learn to exploit, human players change constantly and are more dynamic. And CS does not have any "easy buttons" to even the odds for everybody. The best player is the best player. The worst player is the worst player. This makes it more difficult to get into it, but also more rewarding once you are.