Maybe your to-do list isn't ambitious enough
There's a lot written about to-do lists. How to do them better, why you shouldn't do them at all, ideas for taking stuff off them, ideas for adding things to them and so on. It's a popular topic in the productivity literature.
I'll admit, I'm a little obsessed with these articles and generally click on lots of them.
So, I couldn't resist an article titled Leonardo's To-Do List is Much Cooler Than Yours. It's a fun read. And I think the takeaway is that the issue is not how much is on your list, but WHAT is on your list. Is your to-do list interesting enough? Do you look at it and think "Yeah, I can't wait to do these things" or do you look at it and sigh?
Before you spend a lot of time writing down what you HAVE to do, think about what you want to do. Really, really want to do. Then write those things down. Now you will have a to-do list as cool, as interesting, as ambitious as Da Vinci. Try it.