Last year is certainly hard to compare, but this is something you can go back and look at over years. We can find a running back from the fourth round on because it has been done, but it is neither easy nor absolute, which is what we get in the bad habit of thinking when it comes to the draft.
It's a little like believing that you can easily find a corner in any round because we found DaRon Bland in the fifth last year, while ignoring our recent third-round (Wright) and second-round (Joseph) failures. I consider a fifth-rounder like Bland playing as well as he did a bonus, while some seem to consider it an expectation.
We were very fortunate with Pollard, especially when you look at all of the other backs drafted that year in the fourth round on, and maybe we'll get lucky again if we don't draft one until the fourth on this year in a RB-rich draft. But that shouldn't be the expectation because the numbers don't support it. If we find the diamond among a bunch of trash, then we should be very grateful. And that goes for any position.
Since 2016, we're essentially 6-5 in the fourth round (50-50 shot). Of course, sadly, depending on how you look at it, we haven't been much better in the second round over that time period ... some of those players stuck longer because of where they were drafted, but didn't turn out to be what you expect with a second-rounder (Jaylon Smith, Chidobe Awuzie, Connor Williams, Trysten Hill, Trevon Diggs, Kelvin Joseph and Sam Williams).
This is one reason the Joneses use (or lack thereof) of free agency is so frustrating. You just don't know what you are going to get in the draft and you have a 50-50 shot at best of getting it right.