Cretheus would have most of the same disavantages than standard cruisers, yes. But they would be also overall cheaper, require MUCH less crew, would probably have a better subspace mobility (AFAIK, at least in BP, smaller = better subspace mobility, sprint jump drives aside) and also present a much smaller and faster target for enemy capital ships. Which basically compensates for the lack of anti-capital ship weapons (noone will regret the SGreens) and overall vulnerability to enemy fire.
Like fighters and bombers, and contrary to corvettes, those things are expendable. Better have a small ship (or even a handful of them) with small cost and small crew (probably numbering in a few hundreds at most) to sacrifice than a fully-armed cruiser with several thousands on board.