I'll take the minority side a bit here, and say this is a pretty fair deal. I think Kittle is a lock to come down(single season records are never repeated) and Johnson should be a little better. It'll probably depend on where that 2020 1st ends up.12 team PPR not involved:
A- gave up Johnson, David ARI RB
B- gave up Kittle, George SFO TE, Year 2019 Draft Pick 2.08 and Year 2020 Round 1 Draft Pick
If it were Johnson for Kittle and the 2.8, I'd prefer the Johnson side, and I don't even really like Johnson.