Well, Opinions are good, but are there any observations out there?
The original question is a very well-phrased one.
I think just about everyone can agree that there has been liquid water on early Mars for some of the time, in many places. The question - was it *enough* for life to develop.
Personally, I suspect that if we focus on subsurface life, then the answer will be "yes", but it is not guaranteed. As they say, "more work is needed", but at least we're now asking the right sort of questions, imho...