I think you are missing factors to the equation here. For example you can say Watkins didnt work out because ee gave up a 2 and only got back a 3 but he did play 16 ( I think) games in 2017 so that performance counts towards the rams side of the ledger. What would have the rams looked like in 2017 without him? Maybe not as good. Maybe they dont make the playoffs. And then did turnaround in 2017 play a role in winning 13 games in 2018? Personally I think he played a part in the resurrection of this team.
Same can be said for Fowler. By making that trade we get him for at least 2 years. Plus they may not go to the super bowl without him hitting brees in ot to cause the int.
Bottom line for me is that you cant just count draft picks to determine winners and losers. You need to account for their performance on the field and the intangibles they brought to the team.