This is true, Pace won the trade. And he should have traded up if he had any doubts. But that doesnt mean that what he gave up was a bunch of role players/special team players. He gave up a borderline first rounder, not some scrub special teamer like many here believe.
You are right to a certain point. The 3rd and 4th rounders have some value separately and some value together.
If Pace had not made the trade and somehow had gotten Trubisky at #3 (which I don't believe that he would have been available), he would have had the 3rd and 4th rounders in 2017. If he did not use those picks to trade up, he would have most likely have gotten special teams players and backups. Simple fact.
If he had used those picks (plus the 2018 3rd rounder) to move up, he would have had a much better chance of getting a starter with the low 1st or high 2nd he would have gotten for all the picks.
It all depends on if he makes the trade up or not.
But, yes, all draft picks have some value.
Heck, even UDFAs have value. As an example, there have often been multiple UDFAs going to most pro bowls. Sure, a pro bowl is pretty insignificant and is often a popularity contest. But consider that UDFAs don't win popularity contests and have to outwork everyone else to be invited to pro bowls.