Is there such a thing as too much vanilla?
How much is too much is a totally subjective thing. Yes, there is such a thing as too much, but where that point is will vary among tasters. There is no objective question here to answer. No one answer to the question will be "correct".

I really like vanilla, and I like flavors to be on the rich side, so I tend to be a bit heavy-handed with vanilla. A few (very few) times I have been surprised to have that heavy-handedness criticized. Why would they not like my amazing vanilla ice cream? They experience vanilla differently than I do. What is ideal for me may be overdone, even cloying, to my neighbor.

So, when it comes to various flavorings (vanilla is just one of many), get to know your own "likes" and what your audience likes. After that, you can ignore what the recipe says and just do what feels right to you, knowing your audience and the potency of your ingredients as well.