I'll have to do research on whether the President has the authority to codify anything, mostly to check the rules on that. Can't speak on marijuana because, honestly, it's not on my personal care list so I'm a bit more ignorant. Student loan debt though, he tried...right? Got turned down and has been working towards different paths. Seems like that one is in progress. Not sure we can blame him there.
The president can't make laws but he campaigned that he would work with legislative branch (both sides of the isle) to get it done. However, he hasn't seemed to prioritize that issue at all. He did have some bipartisan wins with $1T Infrastructure bill, CHIPS, PACT (Jon Stewart should get credit for that one) and some other wins, but the main social issues he campaigned on that touch most people's lives directly haven't had much success. Doesn't help that he's completely out of touch with economic reality for many and reluctant to take on corporate price gouging.