This sounds like a technology problem for which a public blockchain is but one possible solution. Surely other append-only log data structures exist which could step in to fill this void.
AFAICT the main issue with crypto equities — and all other similar constructs — is what happens when a court of law overrides them. If a court says your ex owns half of the shares in $WALLET, but the blockchain doesn’t, and $COMPANY which issued the shares is also subject to the whims of the court, then what are we to do about this?
OTOH maybe this rabbit hole really just never ends until courts are also somehow replaced by a public blockchain, likely at the behest of the very biased investors who stand to disproportionately profit from this game.