When did Yahoo Answers start to go downhill?

I personally think it was around 2014 when that started happening.

Over the Last couple of years 

Shortly after the beginning.

I don't think it ever was managed properly. Most suggestions to make it better were ignored

I disagree that the format change caused the "site" to go downhill. Had site maintenance been done regularly, the format change was just a hiccup. What started the trend was when Yahoo was having internal issues and YA was not being properly maintained. Glitches and technical issues weren't being dealt with, the useful feature of L7s being able to relocate misplaced questions was horribly abused, and then Yahoo was bought by Verizon, and largely ignored for quite a while (until multiple spam bot attacks nearly brought down the site in 2018). Lack of oversight by Verizon allowed trolls and site mis-users to flourish. The more technical issues and trolls, the more quality users jumped ship. It got to the point even advertisers didn't want to waste ad dollars on YA due to the poor quality of content. 

funny thing about band wagons they don't form a wagon train YET there are so many of them it becomes sort of like a no driver car with no passengers driving in the car pool lane...

N.Shadows

Society went down hill 

Yes, it started going down in 2013 because they changed the format.