When Biden was elected, Dems controlled both houses of congress. What stopped him from pushing his public option plan then?

This is completely false. They had control of the House, and a tie breaker for the Senate. But that didn't matter much because they need 60 senators to pass legislation without Republicans impeding.

What is stopping him from pushing to deschedule cannabis completely? Even if congress gets in his way, people would give him massive credit for actually trying.

It would be the judiciary that gets in the way as well as Republicans. You'd have people saying Biden is an idiot and only doing this to make it seem he's trying while not actually accomplishing anything. He's making meaningful progress now. Congress is who can actually fix our marijuana laws in a federal sense.

You say we need to elect more Democrats to make bigger steps, but we did that in 2008 and 2020 and still we get baby steps. Why?

Your premise is wrong again. If you have few Democrats in control you get baby steps. If centrist and progressives had the house, and 60 senators and the executive branch, larger steps would be taken. That's not happened in about 24 years or longer. Republicans have had that more times so you can see the progress they've made at bettering out country these last 24 years.

If the president is so powerless, then why are people worried about project 2025 and "dictator on day 1" Trump? Surely they must be confused, because the adults in the room like you know that the president is actually unable to pass meaningful legislation.

For the same reason it's easier and faster to shoot someone in the face than it is to arrest them, put them on trial and imprison them, Trump isn't going about playing by the rules, and he has many Republicans supporting him. If Biden breaks rules, both Republicans and Democrats would step in to fix that.in addition, Trump doesn't care about what will last, short terms goals are fine with him. Biden wants legislation that will get passed and not struck down by a conservative court.