This is a good article it is true to the sense that Google does make many changes all the time and does not give a true indication to what has actually been changed rather then just a line on a blog post about a tweak.
In regards to your comments about "SEO/ Snake Oil salesmen"
I think the problem is many SEO's in the market are just people who have no experience in the field who come in and set up a company, they only offer local search or something else very basic which will cut corners because they have read it in a eBook, too make a quick buck, these are the people who get hit the quickest after these updates because they cut corners for short term gain.
If you work in the Enterprise space their are always going to be clients who need help because it goes more then just silly tweaks you have many advanced areas to work on, clients are lining up for 30 pages audits/ on going consulting on a daily basis/ advanced link building ect ect