Thing is: You don't have to be on par with Slack. If that chat is "usable enough" but integrates well with the rest of the system, this can be a swelling point: Directly reference the tickets in a discussion, reassign, update, ... in a native integration.
With such an "Enterprise" system the choice of the chat tool is a lot more a too down decision, than a chat in a social group.
And it isn't like slack is perfect in all regards either ...
The concern wouldn't be if huly chat integrates well with the rest of huly project management, video calls, docs. It would be all the other services your company uses like pagerduty, salesforce, HR apps, etc where Slack has become the "hub" for everything to integrate with.
With such an "Enterprise" system the choice of the chat tool is a lot more a too down decision, than a chat in a social group.
And it isn't like slack is perfect in all regards either ...