I was ecstatic that I finally finished the first draft of my novel and was excited to read it through

Isn't it good practice, after finishing first draft to just lock it in a cupboard and not look at it at all, for weeks, then after that come back to start the process of revision? First draft is just that, surely? Don't judge it too harshly just yet, I'd suggest, and don't read it back until you've got distance from it.