Realistically, I only see 3 risks using Keeper: my device has malware which lets them grab my passwords from my clipboard as I copy them, malware that lets them take control of my device after I've unlocked my password manager, or if the cloud storage is completely wiped out in some freak accident.
1 and 2 are risks for anyone using any password manager. And 3 is extremely unlikely since they use AWS for storage wirh multi-zone and multi-region redundancy, and certainly much more reliable than self hosting.
The risk of actually having your passwords cracked, even if the cloud data is leaked, is practically 0 as long as you have a decent complexity and length master password and 2FA enabled. And the risk is just as low with a MITM attack or other network based interceptors because of the ZK architecture (as you mentioned) and high encryption used.
Anyone promoting other password managers as more secure either aren't considering the risks to data loss due to self hosting or are buying too much into their password manager's marketing. I think it's totally reasonable to prefer other options due to feature support or subscription price though. A couple of features that Keeper had that made me choose it were:
Ability to create Records which allows me to store anything including files. This allows me to upload sensitive records like tax returns or other documents you'd traditionally keep in a safe or filing cabinet.
Family plan that makes it easy for me to share passwords with people on my plan (great for things like streaming services). This brought the price to a reasonable level.
There might be other password managers now that support these features, as I haven't kept up with them. I subscribed to Keeper about 6 years ago and haven't had a reason to switch. I'm open to suggestions if people know of other managers with better features.