You don't have to download Discord, you can simply join in online (no downloads necessary). Google+ is a rather bad way of doing... well anything that isn't related to Google really...

This is also true. I personally like the downloadable version of Discord. Auto-updates, and there's less to go through with app Discord.

If you're still not keen on it, so be it, whatever your opinion may be, but if you are not trying, how can you judge properly?