Before I became a doula myself, I think back to a time before I ever even knew what a doula was.
I think of the birth of my first child. I thought the same, that I had a MW who supported my birth plan, I may not really need a doula. I'm educated, etc, I felt prepared.
But, birth has a funny way of surprising you sometimes. And if you are a first time Mom, expect to labor longer at home. I didn't know it at the time, but my daughter wasn't positioned properly which made for an intense loooong early labor, before it was even classified as active labor by my MW, and she blew me off. I would have given anything in the world to have had a doula with me at home at that time. Someone with the knowledge to have been able to spot the signs for a malpositioned baby and who could have given me and my partner tips to try and spin the baby, allowing labor to progress more efficiently.
A doula is not to take the place of a partner! But a doula can be a great knowledge base for those times when something unexpected comes up. They have training and skills to help you and your partner through. I know it's best to think for the best and that you will have an easy labor, but it doesn't always go that way. I regret beign stubborn and not seeking a professional to help out with ideas when I was exhausted and stuck.
Just some other things to think about.
Also, a doula is as hands on or hands off as you need. Maybe you could even find a doula that would have a plan to just be on-call for knowledge and there in person if you found you needed/wanted it. They can also field a lot of prenatal questions. I know the most common times I've been contacted by clients is in late 3rd tri when braxton hicks come more frequently and look to me for advice if they may turn into something, or if they are uncomfortable, what can they do. I've also had clients with babies that get into painful spots during third tri and the useful spinning babies knowledge and tips works just as well then, as it does in labor and they are very grateful I could walk them through what to do so they could sit in ease again. :-)