I wrote a sentence,
"It was not always effective but painstaking and sometimes seemed like waste of time."
and I wonder whether the words "not effective" and "painstaking" could be connected with the conjunction "but".
I'm confused because it seems quite natural for me at the first glance, but I learned that "not effective" and "painstaking" both also carry some negative meaning.
Does this sentence sound unnatural? Or maybe I should use other conjunction like, for instance, "and"?