Let's be honest with this--the "controversy" probably had very little to do with the decline. Most shooter fans probably had no idea any of that was even going on. They just did a poor job of making people want to buy it overall. Compared to BF1, it did not generate any kind of buzz.
These military shooters being yearly releases really burns through possible source material quickly. They're going to have to get creative.
Battlefield isnt a yearly release though.
Hardline might not have had a number but I'm still going to count it.
Otherwise, you're right, though I don't know if it makes a lot of difference. There is still a military shooter released every year and it's going to keep getting harder to find a "Modern Warfare" or a "Battlefield 1" that really gets everyone's attention.