Of course, the technical backbone of a product is rarely a user concern. But, changing the store allows for new design decisions when making the schema that are not tied to the old (IMO) technical debt of the KDBX format.

Users have wanted proper custom entry templates for years in order to input their card details into the manager. BitWarden, CodeBook, and others all have this built in without needing to fiddle with attributes and autofill to make it work.

I think a major change like this is worth it when we consider the KeePass of the next decade or two. This is genuinely my most important file by a longshot. Basing it on SQLite is just the right move for future proofing.