Seems a little harsh! Prometheus is a big project thats been around a long time, and I'm not expert in it, but I don't think it's aspiring to do incident notification or APM, is it? I think it's just metrics. Maybe more constructive would be to provide some specific things that were unclear or confusing to you in the overview, and/or to suggest that they integrate with Prometheus for the things it's already excellent at and avoid reinventing them? Dunno, just my $0.02, but they're both go projects and it looks decent at a glance to me, probably just using material I think?
Anyway, I think open source stuff sometimes needs constructive criticism but should always be appreciated first as a contribution to the ecosystem even if you're not personally planning to use it.