Come on that's not even a hard one. Congress was split, not enough votes to break fillabuster, meaning Dems didn't have enough votes to codify Roe after the conservative Supreme Court, thanks to Trump 1, repealed it.
To fix the Supreme Court would take a supermajority which is unlikely. Codifying Roe will take much less. They should have done it during the Obama years when they held a fillabuster proof majority.
If you want to undo the system you should at least have a basic understanding of how it works