Hey karma or feed!
We have Rioters in various areas of expertise. I'll use myself as an example for this.
I'm a part of the skins team, so my knowledge is heavily grounded around the creation/development of skins. I'm most likely to post in 'Skins & Champion Concepts', 'Story & Art' or 'Report a Bug' (when bugs are skins-related) because these are the conversations I can offer the most in when it comes to informing, answering questions, or discussing player concepts for new skins. That said, I wouldn't personally hop in threads on 'Gameplay & Balance' because I don't know too much about why changes are being made, or even how to balance a champion.
Some Rioters work on things not directly to the game - maybe they work in accounting (Not Steve, though. I mean, that's definitely not Blitzcrank), or an area of Riot where most board subjects don't make sense for them to post in. They're still making an effort to engage with the community where possible, even if that means jumping in a 'Memes & Games' thread. That said, we're players just like you, and sometimes, we just want to have fun (especially on the weekend)!
I can understand why you're frustrated, especially when there are issues at hand.
That said, the boards are growing, which means it's becoming a lot more difficult to respond to every board post. If you don't get a personal response, don't take it, well, personally. Several groups at Riot cruise the boards several times a day to see what's going on - especially in the Report a Bug section. While you may not see a response to every thread, we do read them all, and the issues are looked into. In cases where there may be a serious exploit, you may not see a Red post on the issue for two reasons - a. we're trying to resolve the issue ASAP, and b. we don't want to get more visibility on the subject by having the post end up in the Red Tracker.
I agree that there are issues still occurring in the game, some serious enough that it prevents players from patching. Let's talk about the portion of players who couldn't patch Patch 5.13. dArtagnan created a post in 'Help & Support' with some troubleshooting tips when it came to trying to resolve the issue. Rioters, as well as the Wrenchmen also offered additional support in the comments, if players were still having issues.