If youre looking for something more than just a group then I will recommend you join Reddit. There are lots of Bitcoin and altcoins enthusiasts there discussing on very interesting topics. You will also be getting updated there regularly there with lots of topics to engage in. If youre looking for just a group that also has a lot to offer, then you can go for Telegram. But in Telegram you wont be able to join any group without having the link to do so. Before you join a group, someone will have to give you the link to do so.
People having admin rights in the telegram channel and group can only able to share the joining link of the concern group. Others will not be able to do that. As you telegram is the best place for the project mates to discuss about it.
There are some other option also recently used in wide range mate. I suggest to use the Discord or slake channels for the communication medium.
If there any new implementation such as groups option here in this forum means also here all bitcoiners will love it and go towards it. No more we need the help of the social network mediums.