In my opinion the best app similar to Slack but organised around the thread communication is Twist (https://twistapp.com/).

It's disappointing that it's so hard to convince the companies "management" to switch from chaotic Slack communication to something better for async and organised communication because clients are used to Slack...

The same applies to Discord as it's just the most accessible way, everyone uses and it's just largest common denominator regardless of the chaos in most of the channels, hope the threads will clear some things up when people use them, and not like in the Slack where everyone just paste response in the channel instead of the threads.