TC and SE session 3 Homework Question 3

Hello everyone! I hope someone can help me with this one. This question is from the homework on TC and SE session 3.

Lavoisier’s experiments were groundbreaking and his theories fundamental to modern chemistry; this mattered little to his contemporaries, who dismissed him as but a ______

So, Greg explained this and I got the first two blanks. For the last one he said “novice”. I get that Lavoisier’s contemporaries did not appreciate him and called him a “beginner”; however isn’t there the word “BUT” ? Shouldn’t it be like that:

They dismissed him as a beginner = They dismissed him as but a genius

I hope I could make myself clear. What I mean is, isn’t the word “but” should make a difference, an opposite meaning? When we say “you are anything but honest”, don’t we mean “you are dishonest” ? I just cannot get my head around that.

Hey, are you use the “but” is supposed to be there? It reads really weird. Can you show the screenshot of the question?

Here you are

Wow, apparently that’s a thing, TIL

https://www.reddit.com/r/ENGLISH/comments/178m0p9/is_but_a/

Apparently it means the same as “nothing but” which doesn’t do anything. So there’s no contrast with the “but”.