What's the purpose of a tool? To help you get things done.
In the case of SEO tools for beginners, it would be to help them get "SEO done".
Search Engine Optimisation (not online marketing, social media marketing, or pay per click) tools, therefore are going to help you optimise for search engines, aka -improving your traffic, therefore your rankings on organic search.
There are tools to tell you how you are doing currently (historical reporting).
There are tools to tell you what you are doing wrong with your site (site audit tools) and tools to tell you what you are doing wrong with your backlinks (backlink analysis tools).
There are tools to tell you what you could be doing (keyword and competitor analysis tools).
How long is a piece of string?
None of these tools are worth having if you don't have enough knowledge. Tools are designed to help make your life easier, by automating what you already know how to do, and thus saving you time.
Tools are not the same as education. They are not going to impart the wisdom of the sages. In fact, if you choose the wrong tools, they'll steer you completely down the wrong path.
None of the tools are a replacement for education and experience. They won't tell you that those other 10 copies of the site, running on the same server, but different domain names, are poisoning one another.
Beginner tools aren't going to tell you that your site was hammered by a Penguin, or that your suffering from a bad Panda. If you do get lucky enough to find one that will overlay your WMT data with a Google updates calendar, they won't tell you which of the backlinks were the cause, which pages were dupe or over-optimised, won't tell you how to know whether you should do removal requests/disavow or whether you need to do a reconsideration request.
Yes, a beginning SEO practitioner must start somewhere and move from nowhere to somewhere, and then onward, upward.... Shoving a tool in the hands of a beginner isn't going to make them better at their job - just faster.
The best tools are training and testing. Read about it, think about it, try it out, then believe that which is useful and forget the rest.