The foremost item in that list is relatively new to the website as a whole, and it's at ends with the rest of the website. There's plenty of infighting about people from that camp staying in their camp and not bringing their garbage to other boards, but that never ends well because of the fanatic dogma that the people in that group subscribe to. However, the latter two items in your list have been present since day 1, although there's an actual homosexual board for people of that group now. Overall, the entire website used to be better 8 years ago, with some of the last good events and posts on that site being around 6 years ago.

> What are those communities like?

Die-hard enthusiasts, a smattering of experts, and people somewhere in between: all on the website to goof around. Asking to be spoon-fed knowledge is a sure-fire way to derail a thread into people telling you to buzz off (I've used kinder words here) and google whatever it is you're looking to know. However, if you demonstrate to the posters your competency by speaking on the material, you'll be in good company. Sometimes, that's not enough. Lurking was a HUGE part of the website, and people used to be shamed for being from another community and treating the site like their other community. Nowadays, not so much. Again, it was somewhat better years ago, though the past contained its own share of troublesome repeat posters.

> What’s the benefit compared to Reddit/wherever else?

You'll get actual opinions from actual humans. No one has a Reddit board mod breathing down their neck, ready to shadowban posters for "violations" at their whim. In the past, posters have been surprisingly generous, offering books, games, software, and their own FTP servers for sharing. Because of the "die-hard enthusiast" air, there's still a sense of holding the content of their hobbies to a higher standard. I've found many people aggressively funny in the past, but nowadays many seem to be slaves to the board stereotypes and in-jokes. You won't see any "I CANT EVEN xD" like on Tumblr, threads aren't a popularity/points contest like they are on Reddit, and you won't see any posts going "DAE MEMES?!" like on both of those sites among others. Posts on 4chan are also way less self-serving because of the culture of Anonymous, while it's a common (and sometimes correct, based on some of the posts I read on the programming boards on Reddit) assumption that everyone who posts on Reddit is looking for an ego boost in some manner. Note that the picture I've painted of the posting on 4chan is not always like this.

To access the benefits, there are a few hoops to jump through: be able to privately/mentally dismiss someone as a fool and move on with your life instead of allowing yourself to be bogged down by what they post (someone else will inevitably end up fighting that person anyway), find the boards YOU want to browse (using 4chan as a whole is not a prerequisite to the site), lurk for some time before you post, and be aware that many of the boards on 4chan just aren't good. Usable boards in the modern day include: /vg/ for repeating threads on specific games, /tg/ for traditional games, /a/ and/or /jp/ for Otaku culture, /o/ if you like cars, any of the smaller or less traveled boards like /trv/ or /out/. For most of the other boards on 4chan, you're better off just using Reddit these days.