I have received a request to referee a paper submitted to a journal I hadn't been aware of before. The paper is in my area of expertise, and I've been working in the field for a few years and read arXiv & major journals (nobody I know has published there, as far as I know). Though to be fair it is published by Springer Nature and has an impact factor of about 2.5.
I'm reluctant to accept the request, because (i) it would cost me time, (ii) I never read the journal, (iii) the abstract is badly written (grammar mistakes, and it's of the form "We use standard methods to calculate some properties about a standard system, which have been discovered in many slight variations before").
Is it okay to reject review in this case? I'm afraid that my judgement may be off.