Indeed, not only is this only looking at the very broad end results of what is seen to co-vary with age in a regular way completely agnostic to mechanism, it is looking only at gene expression in peripheral blood, one very highly specialized (to the point of being a liquid) tissue type.

Yeah it doesn't say much. For one thing I'd say it's just about all of the genes that are differentially expressed, if you look hard enough. Regardless, that doesn't tell us how many of them really matter with respect to the things we care about, how many causal factors are at work, or how difficult it will be to fix. Doesn't rule out a single silver bullet aging cure (though other things probably do)