Absolutely. Flagging is no less useful now than it was before; only the process by which flags are handled has changed.
Let's use this answer as an example:
Could I ask then what is the comparable "blocking" ability of lead, zinc and regular carbon steel (ie steel used in general construction), In simple terms, for example 1mm of lead is the same as ?mm zinc and ??mm steel????
Clearly, that is not an answer. Flagging it as such puts it in front of the moderators and other users via /review/low-quality-posts. If multiple people flag the same answer, it gets pushed toward the top of the moderator queue. It also gets a bit of additional weight on the side of "delete" in /review.
In this case, either moderators or reviewers can delete the answer - this means the flag will be handled regardless of whether or not there are moderators or reviewers active on the site - the post will be dealt with by whoever gets to it first. In this case, both queues contributed to handling the flag, with a reviewer leaving a comment explaining why this was not an appropriate answer and a moderator following up by deleting it.
In some other cases, the flag may not be able to be handled by reviewers. These flags enter the moderator queue only, and remain there until a moderator is able to respond.
As a 10K user, you're now kept abreast of the state of /review via the number at the top of the page; if that number isn't budging for days at a time, neither moderators nor reviewers are keeping up and flagging isn't working - maybe ask around and try to find out why.
A pocket guide to flags
As a reminder, the following flags are available in various situations:
Very Low Quality: used to call out a question or answer that is abysmally bad - not necessarily even incorrect, but impossible to understand or utterly irrelevant. The sort of post that would embarrass you if it showed up when you were showing off the site to a peer. Each "helpful" VLQ flag comes with an automatic downvote, compliments of the system. Only available for posts scoring <=0.
Not an answer: used to call attention to posts that do not even attempt to answer the question they're posted in response to. Follow-up questions, commentary on other answers, rants, etc.
Offensive: posts that shock the proverbial conscience. Generally, such posts will have other problems as well, which might otherwise result in them being closed or deleted - but in this case the author has gone out of his way to make his work odious. Each flag generates an immediate downvote from the system, which will be retracted if the flag is declined.
Spam: overt self-promotion. Can be anything from mechanically-generated offers of discount handbags, to someone obnoxiously pushing their tangentially-relevant blog in lieu of actually answering questions. Like Offensive, you'll know it when you see it. Also generates an automatic downvote.
A sufficient number of either Spam or Offensive flags on a post will cause it to be instantly removed, locked, and the author's reputation docked 100 points. If you find spam inherently offensive, just pick whichever option seems more appropriate.
Other: You're not quite sure how to categorize it, but something is rotten in the state of Denmark. Hopefully, an experienced moderator will be able to sort it out. Requires entering a description of the problem - be specific!