I would whole-heartedly follow Dr. Seuss.

An agnostic is a bit different. There are degrees of certain things. If you are talking about degrees of belief, then, yes, agnosticism has a place in the conversation. Too often people apply false opposite to things.
For example, cold is not the opposite of hot. Not hot is the opposite of hot. But, you can put them on a continuum. That continuum would be directly related to degree of temperature. The question of the continuum is not "is it hot?" That is the question of the opposition. The question of the continuum is "what degree of temperature is it?"
In the realm of opposition, atheist is the opposite of theist. There is no getting around it. If you are not a theist you are an atheist. Plain and simple. Now, if we want to form a continuum, then, yes, people will measure their degree of belief using these terms to exemplify the strength thereof.
It might help to note that an atheist is someone who holds no belief in a deity. That applies to
everyone who cannot say they believe. That includes agnostics. Because if they aren't sure, if they don't commit, they don't believe.:)
(Wow, we are a bit off topic now, huh?)