I don't go on social media for that exact reason.
It does feel terrible and purposeful when people seem to be purposefully ignoring you
Some things I try to remember when I start feeling like this.
1. I have no clue what other people are actually doing thinking or what their intentions are.
2. If someone does not respond to me right away or in a bit, it most likely has to do with them..not me.
Maybe they are busy, maybe they just left the app on open, maybe they always are signed in but rarely on, maybe they walked away for a while, maybe they are dealing with something they feel is more pressing atm, maybe they just don't feel like chatting right now, Most definitely they are focused on their $#!T first!..most people are.
3. I did not always feel this way.
Idk how old you are, but I am not ancient and I can remember a time before social media and smartphones cellphones where if I tried to call someone and they did not answer..I did not take it personally...nor did I expect that for any reason were they required to pick up or call me back the moment they say that I called..nope mostly I just figured they were not home, busy doing something else, talking to someone else, just didn't feel like talking at all...and almost never took it personally!
3. It really isn't any different..the only thing that has changed is our perception skewed by the overwhelming amount of information our current technology provides..and it is not all good! It is so convenient and helpful in many many ways..but it terrible for our self esteem!..
My advice is when you start feeling like this...take a tech break! Turn off your devices or sign out of your apps. Set them to do not disturb, walk away from them and go do something else for a while! Watch TV, read a book, go for a walk, take up a hobby, any nontech related activity you enjoy.. I think you will feel a bit better after.

And if there are some people who truly NEVER answer or respond like not even once a month...They are not your friends..axe em.
My best friend and I can go over a month without talking..but it doesn't feel like a slight.
Hope something I wrote helps
-LITW