Sure you dont own it, you have a right to be angry.

But how does that justify you using something someone spend their time on?

I mean, you dont have to use it if you dont like it, but you do, they spend their time and give you terms to use their product. Thats it.

I think Matrix is the most suitable alternative. For me at least. The Element web and desktop app is almost on level with discord and on matrix.org and other popular instances you get element call too. Plus people already use it.