Yeah when I say go out and meet people in the real world, I don't necessarily mean doing so solely to meet girls. I just think it's important to be social in general, and I think it will help inside and outside of dating.
Throughout highschool and most of college I was very introverted. Over the past few years I've made an effort to work on that by forcing myself out of my comfort zone. It has paid off tremendously. I've been doing great business networking, meeting new friends, and having an easier time meeting girls. I still don't have all that much desire to go to bars and clubs (it's more than okay to not live life for the bar/club scene), but at least I'm not as uncomfortable when I do go to them and I can enjoy myself when I do occasionally go. And if you ask me, going to bars/clubs won't make you more interesting; I'd say you'd be better off picking up new hobbies or having an interesting career. New hobbies are also a good way to meet new people.
In regards to being friendzoned, I think online dating and 'IRL' dating can differ in important ways. With online dating it's important to note that, because you're both on an online dating site, it's usually safe to assume you are both single and looking to date. It's also easier to get to know someone before the first date -- you have a whole profile to read and you can chat some to give you an idea of whether or not you're interested in each other before you even meet in person. So you might be able to get away with being a little more 'friendly' or neutral at first, but I think it still helps if your communication is in sync with your intentions (and remember, your intentions are to meet romantic partners).
When meeting new girls in the wild, I think you have to approach things slightly differently. First, whether or not they're single and looking to date is totally up in the air -- therefor, it's more important to make your intent known. That way if they're not single or interested they can make that fact clear and you won't waste your time. Trust me, I know how strong the tendency may be to become friends with the girl first. You want to get to know them, then take it from close platonic friend to romantic relationship later when you confirm it's worth a shot. But on a practical level, that is hard to do. I think it's much more effective to be upfront about it. As a bonus, it also makes you seem more confident because you're sticking yourself out there. So to conclude: if you're getting friend zoned, I think it's most likely because you're initially coming on as a friend. You aren't clearly communicating that you are romantically interested from the start. I always recommend that instead of saying "we should hang out sometime, can I get your number?" say "how about a date sometime?" and then get her number; that way, everybody's on the same page. And again, it shows you have confidence.
I don't necessarily think online or IRL is better than the other. Whether you get to know them before or during the first date is inconsequential, but as long as you understand how to approach different situations I think you'll be better off.
Also somewhat related: Some girls want platonic guy friends. If they meet a guy who is being very friendly but not romantic, they may get their hopes up that they've met a potential guy friend. Then weeks later when you want to move it to the next level, they're caught off guard and they can even feel like they've been tricked. They are always worrying that their guy friends will suddenly flip and want something romantic. There are some girls who use guys and friendzone them intentionally, sure -- but there are also girls who aren't so evil.