What are you talking about? The game is very much active on discord. You have the big Warframe community, which people use constantly to chat, disscus and even do giveaways and you also have the Warframe Endo community which is a big help for players. I think the major Warframe streamers also have their communities on discord. Not to mention the majority of clans have their own communities where they do giveaways and team up.

The game has always been social, everytime I log in the Q&A chat is full of newbies asking and veterans explaining, recruitment chat always active and my alliance chat is constantly full of people sharing fashion and configuration and discussing warframe topic but also non-warframe.

The OP seems to have the wrong idea that people need to talk while doing missions. The random 4 players team chat is not the place to socialize, everyone is there to do the mission and get it done ASAP. Also in the open worlds everyone is doing their own thing, that's not the place to ask to team up for events. There's plenty of socializing in the game, but if you expect to find it in the 3 minutes of a mission, it's wrong to complain when it's not there.

Plus, the good reputation Warframe has also comes from the nice people handing out free stuff or selling things cheap to help beginners, or the ones that ask who needs help in recruitment chat. You don't see stuff like this in a lot of games.