There's already Zulip, Mattermost, and many others. Building a chat application should be considered a tar pit problem IMO. A lot of success relies on network effects and familiarity, and the product looks deceptively simple.
It's unlikely you can build one that is better than Slack without years of investment. Even if you do, it's still an uphill battle.
It's unlikely you can build one that is better than Slack without years of investment. Even if you do, it's still an uphill battle.