Como dizer "Não sei dizer" em inglês

Could be different situations:
I don't have an opinion on that/this (topic).

I don’t think that’s for me to go into.
Evading a "prepped question" (a.k.a. Suggestion) trying to compromise you, give a bad opinion about someone else, etc.

I'm not informed enough to have an opinion on the matter.

I am sorry I don't know enough to have an opinion on that.

And so on and so forth. But be ready to be pushed around to "have an opinion", no matter what.

With this topic, a buddy from the Forum recalled Gloria Pires participation in the Oscar broadcasting/commenting: I have nothing to say, I didn't watch the movie(s).
Then, yet another question trying to engage her in the commenting:
Gloria did you like Divertida Mente? The answer - "I didn't watch it."
And again, do you think Lady Gaga is going to take the award?
"I am not able to give an opinion “
Gloria is an excellent actress, and the next year she was greatly missed, she added a lot of fans to her fan club, how could I miss that Oscar coverage?

Mas dá para usar "I can't tell ou I couldn't tell?"or I don't have words to describe it or I coudn't tell anything about it or I coudn't describe it ( tipo não saberia te dizer isso ou não sei o que falar, não conseguiria te falar o que penso ou acho do meu emprego) É que a pessoa não tem palavras para descrever o próprio emprego ou não sabe ou consegue descrever se é bom ou ruim, não tem uma opinião formada do próprio emprego ou empregos ou cargo que ocupa.

I couldn't tell could be understood as "não deu/não dava pra notar": I couldn't tell he was really upset
Or I couldn't really tell if he was annoyed or tired.
Eu não podia/sabia dizer se ele estava aborrecido ou cansado.

Somebody asked for a more concise way and less formal. I guess "I don't have an opinion." (on it) would be terse enough.
Of course, there is the evasive "I have no clue" (implicit - "about it" - the matter at hand) or the (perhaps) or "I don't know". Or even the 'defensive' "I don't care".
The original sentence and context could also be simply "not sure" (if his/her job is interesting or not).

It worth noticing that if it is in a job interview or some IELTS question, it's a good idea to bring up at important aspects of the job (even if the job doesn't seem interesting). If you get startled by the question you can buy some time to think by saying something like "that was a curve ball, but..." (find something important done in that job, please).