I agree with the Twitter comment but can't stand Reddit. It's a site that promotes trolls and actively punishes people for being civil. Add to that completely tone deaf policies from the owners and I just cannot support that site. The mods there are also terrible cretins that rule over their fiefdoms with whatever bias they feel wont to.
Most people whom have expressed this sentiment to me have generally not been exposed to much more than the defaults.
Reddit with defaults or r/all is a horrible experience. It is what you make of it though, and if you don't make anything of it then it is obviously not for you. The advice I always give to someone trying reddit is to 1. make an account 2. unsubscribe from all of the defaults and 3. search it for whatever interests you. Pretty much everyone can find something for them, and moderation is going to be variable which I think is actually a net positive. A well moderated sub is a gem, such as AskHistorians, but not every sub needs to be moderated to the same extent as AskHistorians to remain useful or relevant either.
I'm not saying that I've never had a positive experience on Reddit. I'm saying that I violently disagree with how they've handled themselves and their trolling. It's saying Well Fargo Bank has some amazing tellers if you can look past their horrendous policies meant to fleece people who bank there. FWIW HN is literally the only social networking site I still find valuable so I completely respect that your experience and value derived from Reddit may be different than mine.
Yep, that's why I am promoting custom filters. There are so many folks on Twitter who post awesome content but I have to unsubscribe so I don't get inundated with their politics.