[SumAznGuy]

I'm sure the thanks/fail function may have had some impact on people posting, most of it is due to the changing demographics.
RS and IC started off as part of the import car scene. But at the same time, the internet was still young and new.
There was no CL or FB chat groups.
The only thing you had was the buy & sell paper that came out every Thursday or the classified sections in the newspaper.

You came online to RS to chat with other members and to buy/sell stuff on the classifieds.
Now, all the people that would frequent RS have all grown up and have less time to surf RS as well as dedicate some of that time to other forms of social media and online games including, at one point in time, Angry birds, Candy Crush, Clash Royal, and now Pokemon Go.

As long as there is enough viewership that brings in ad revenue, RS will be around.
Once that stops, then they need to take a serious look at keeping RS alive.