SEO for Google - August 2017

Here's my understanding. For all the talk of "links are dead", I believe that search engine position is determined by:

1. Quality and quantity and relevance of incoming links from websites. I believe that these are still slightly over 50% of the battle.
2. Sites are also lifted by social media such as Twitter and LinkedIn, perhaps Pinterest. I believe the Google bot is still banned from Facebook which would also include Instagram. I'd guess that this is 25% of the battle. 
3. Engagement. I believe Google spends a lot of effort to measure whether people leave Google and engage with the site or whether they go to the site and stick.  Another 25%.

Of course, this is a bold statement to actually quantify how I think the engine works. I'll keep postulating. 

Increasing Value of Major Authority Sites.  I think that big authority sites used to count a few times more than minor authority sites which counted more than routine sites which counted more than small sites with some history (lets say some respectable links and more than a year of history).  A decade ago, the links from each level up might have been worth 3 times more at each level of authority. I'd now say that it's a full order of magnitude more important.  So today, the value of links from each of these level is worth 10x more than links from the level below. Or maybe it's 100x. My point is that real authority is much more valuable than it use to be:

• new blog and sites with no real traffic, less than a year, and just a few links: hardly count at al.
• established sites with some traffic, more than a year of history, and lots of ongoing incoming links
• small authority sites.
• Major authority sites.

So many open questions....

• Do Youtube links count in the web links category or the website category? Or do these distinctions not mean anything at all?
• Do youtube links from videos with 10x more views count 10x more?  Do Youtube links' value count more based on total views or recent views or comments?
• Do Twitter links increase in significance based on number of followers of the tweeter? Or by engagement with the tweet?
• Are the percent of front page "local" info known for each set of searches? Does it change over time?
• Does Google consider all the blogger blogs to be sort of the same IP address so there's a decreasing value for each blog that links to a site?