Good question, and one we've had to answer practically on a regulated (banking) data platform.
My take: Databricks + Unity Catalog now covers a surprising amount of "MDM-adjacent" plumbing - golden record storage, lineage, access governance, even survivorship logic if you're willing to write it yourself in DLT/Spark. Where it still falls short of purpose-built MDM (Informatica, Reltio, etc.):
1. Match & merge tooling - probabilistic/fuzzy matching with configurable stewardship workflows is far more mature in dedicated MDM products. You can build match/merge on Spark, but at that point you're rebuilding a product, not configuring one.
2. Stewardship UX - business users (not engineers) need a low-code interface to review merge candidates and override golden records. That's a workflow/UI problem more than a data problem, and it's not what the Lakehouse is optimized for.
3. Audit trail semantics - in banking specifically, "why was this the golden record" needs to be provable to regulators with a change-history model MDM tools ship out of the box. Doable on Delta (CDC + Unity Catalog audit logs) but you're assembling it yourself rather than getting it for free.
Where the lines genuinely blur: reference data management, hierarchies for less-regulated domains, and cases where "good enough" survivorship rules in a pipeline beat the cost of a full MDM license. For core customer/party golden records in a regulated industry, I'd still reach for a dedicated MDM tool with Databricks as the governed serving/analytics layer downstream.
Curious if anyone's tried building a stewardship UI on Databricks Apps - that's the piece I'd want solved before fully retiring MDM platforms.