For a loyal DL customer like myself, the lack of connectivity from SLC to secondary and tertiary Western markets can be frustrating. I get that there's relatively little meaningful volume through them, but it can be maddening.
Folks can call it what they want - whether it's "not a hole" because Delta is such a big international carrier - but ultimately they get that way by doing a lot of flying and being able to connect people to/from as many places as possible. That's why SBN-DTW going away is so annoying, as are some of the other gaps.
I travel to SBP frequently from the PNW and it's unfortunate how little service to that area Delta has.
UA flies SBP-SFO, SBP-DEN and SBP-LAX
AA flies SBP-DFW and SBP-PHX
AS flies SBP-SEA, SBP-PDX and SBP-SAN
DL can't even manage a single flight to SLC or LAX (or SEA). I usually fly to SFO or SJC and (or even a UA SFO-SBP), or suck it up and fly AS if the ticket is cheap enough (which it often is not - fares can sometimes be very high).
In the grand scheme of things, it does not detract from Delta's grandiose route network, but these start to stack up when there are holes like this.