Yes indeed, blockchains aren't suitable for storing personal data. No public decentralised network is. IPFS wouldn't be either for instance. By nature such networks assume no one peer can be trusted. Not the sort of thing you want to trust with confidential information.
This openness is often sold as a feature, for example running your supply chain through a blockchain means there is a publicly auditable ledger of every step, so a company claiming to have an ethical supply chain could theoretically point to that blockchain as proof. This is potentially interesting imo.
Most enterprise blockchain solutions I've seen are hybrid ones. A business can store personal data in a regular database and have non-sensitive data on a blockchain (as per the example above). The advantage of this (outside of the above use case) being that you can run SQL queries on large data sets much faster if that data is stored on a distributed ledger.
(Note: this is what the companies selling those solutions claim. I don't have first hand experience with blockchains in an enterprise context so I couldn't tell you if this is true - I imagine it'd depend on the database and blockchain in question.)
Final point though, these aren't necessarily proprietary blockchain solutions as such. They're more like SDKs businesses can use to build their own blockchains, code their own smart contracts, etc.
Whether this is actually useful for enterprise... I honestly couldn't tell you. I do think the supply chain stuff is interesting. I also think using it as a system to detect counterfeit items is another good use case for businesses. In the past, companies have created apps where you can scan a QR code and it confirms the legitimacy of the product, but counterfeiters just made QR codes that tricked the app. If each unit is tracked on a public blockchain, it should be possible to verify legitimacy with near 100% certainty.