Who trawls the (now huge) database to find the registered studies which never reported? In any case, that could indicate a file drawer problem publication bias or simply that the funding disappeared or a researcher decided not to proceed.
How do you move from very spotty preregistration to compulsory preregistration? It would probably take a coordinated push from all the major funders. And they haven't successfully moved to fully open access publication in over a decade of trying, despite the obvious financial gain to the non-publisher world of winning at that coordination game.
How do you handle work on the margins of registerability? Not all scientific work is testing hypotheses, some is exploratory. Should a quantitative description be ruled out if it wasn't registered? If so, how are reasonable hypotheses for future work established? If not, you have to be extra vigilant to stop people smuggling phrases that imply confirmation into nominally exploratory work.
And the other problem with the replication crisis is that even decently-planned, pre-registered, straightforward studies can not replicate. Sometimes for reasonable reasons (significance was actually by chance, some unanticipated confounder interfered) and sometimes for thoroughly blameworthy ones (rather than p-hacking you can just fudge the data, or make 'accidental' programming errors).
So I'm all in favour of pre-registration, but it's not a magic bullet.