I'm not yet catching up on backread here; just stopped in to ask whether
judaism.stackexchange.com/q/71617 seeks opinions. It asks for "commentaries" (why they have to be commentaries and not standalone texts I don't know, but so be it) and not opinions -- but answerers will find commentaries that say part A of the prayer service or another satisfies criterion X and (here's the opinion-based part) those answerers will interpret that as meaning that A is important, or most important.