For those determined to exit the Facebook ecosystem, the best approach is more likely to be a patchwork of sites and apps that mirror individual features. Messaging is the easiest: apps such as Telegram and Signal offer messaging and group chats, as well as voice calls, with encryption to keep your communications private. Telegram even has a thriving collection of chatbots, similar to Facebook Messenger.
While Path isn’t necessarily a true competitor to Instagram, it has many of the same features. You can capture photos in the app, apply filters, export them to other apps, or post them on your stream for friends to view. Most of the privacy concerns surrounding Path have been resolved, and it offers a very intimate approach to sharing. Rather than imploring you to build an army of followers, Path strives to keep things intimate by sharing photos with the people you care about most. The photo-editing features aren’t as good as the other apps mentioned here, but as a social network it is argueably a better experience than Instagram.
A simple chat (slack style) it's enough. Just having the possibility to send messages either single user or team (#channel). But please don't forgive to give an useful appeal to mobile app (worst error of competitors is, have a good app but totally no mobile friendly!) i would expect to have a similar whatsapp or slack app for messaging within the slack mobile app!