Sadly, the folks who most need to hear this are same ones unlikely to take the advice. And also complain the loudest when their papers are long in review
Chris MacQuarrie
Scientific journal editor here:
If you're invited to peer review an article and you can't do it, please just click "no."
That tells me "this person can't do it, I should invite someone else." Otherwise the system waits 3 weeks to tell me that you didn't respond and I should invite someone else.