Hi !
I’m agree with you, Slack is poor of functionality and community roles, and Discord is growing and can be a very helpful solution on many points :
PRO 
- You can add moderator, mentor, support, … any roles for any users
- You have an unlimited messages, and this is important when you have a big community like Strapi’s now
- Slack is slow… and bug frequently, you can’t chat with many people without launch a call and wait than everyone is connected
- Discord is moving forward to be a professional solution and replace other “pro” tools day after day
- You can parameter your account to display custom name, information, … by discord server or keep your “default” account information
- Only one account allow you to access to many servers (but this can be a “CON” when you need to separate professional / personal account)
- Unlimited channel, and groups
- Instant vocal sharing, useful to discuss with others and join discussion when we want
CON 
- You need to have a Discord account (oh, an other network…)
- You need to upgrade your mind, and try this “new” professional solution, their are flag as “gamer community” for now, and this need to change !
Personally, I’m using Strapi’s Discord server with my “personal” account, and I configure it to share only what I want.
I hate Slack, but I’m using it everyday because of no choice, but Discord doing the same thing, with a better infrastructure and a fairly pricing.
Don’t be frustrate and try Discord !
PS : (In my company, I’m also working on this subject to migrate from Slack to Discord)