I think Discord has its perks, but only if you actually have a reason to use it. It should never be used as a substitute for email or even instant messaging with just one person (we have Outlook and iMessage for that). The fact that you can have multiple "channels" for talking about different things keeps everything organized, which I like. I'm only in one Discord server anymore, which I'm just in because I've gotten to know the people well and it's very small. I'm going to keep Discord around JUST because of that one server I'm in - otherwise, I'd probably get rid of it.
And oh boy, Instagram is a whole 'nother can of worms. THAT may be the worst platform I have ever encountered online. I regret joining, it's deteriorated my mental health - it's actually made my life worse. I would leave, except there are a few specific people for whom Instagram DMs are the easiest way to reach them.