Is Google's algorithm so complex not even its engineers fully understand it?

Is Google's algorithm so complex not even its engineers fully understand it?

Google's search and ranking algorithm have become so gigantic and complex that apparently, not even the engineers working at Google fully understand it. 

Google's search algorithm has always been complex and people always tried to crack the code behind it to make their website rank higher in the search results. This isn't a mystery really, this is how search engine optimization as born! 

Danny Sullivan from Search Engine Land said the following:

Google’s own engineers tell me and others they don’t even really understand how it works. Ultimately, the best way to “rank” for RankBrain remains that same boring thing no one wants to hear despite it being true. Have really good, descriptive content.

But a recent statement made by John Mueller (a trends analysis and webmaster at Google) tries to dismiss all of this:

Source
Of course, Google is trying to dismiss all of this! I personally talked with a couple Google employees at various events and I even participated in an interview with Google. Like any other tech company out there that has certain people that have very specific roles inside the company. Depending on your department you are on a need to know basis and won't get too technical involved with other departments. So I'm pretty sure the most search engineers at Google don't fully understand or know the whole algorithm.

As far as lead engineers go, maybe but I have my doubts about understanding the whole picture on a detailed level. 
Sure, maybe they get the big picture, but what scares me is that the algorithm as grown so complex, that no employee understands it at its full form, this together with the new Rank Brian update which is essentially is artificial intelligence makes me believe that Google's algorithm is unique in the tech industry and some day may take over the world. 

Joke aside this clearly shows SEO experts are limited in their powers. Sure, some SEOs are very successful in ranking websites and do SEO better than the majority but that doesn't mean by any means, they cracked Google's ranking algorithm. If most Google's engineers don't know the big picture, don't expect an SEO to implement miracles. This was for all the SEOs out there to claim they can get anyone on 1st position on any keyword as well as the clients that believe such SEOs exist! 

So, what do you think? Is Google in full control over its search and ranking algorithm, does any Google employee fully understand the code behind all of this or did they lost that ability a long time ago?
Let discuss this in the comments below!