Data taken from FFlogs world race page at May 3rd, 5:30PM PST

Out of the top 20 progressed teams that are logged, the DPS selection is as follows

RDM:16 SMN:6 BLM:1
BRD:10 DNC:9 MCH:1
MNK:15 DRG:12 NIN:8 RPR:2 SAM:0


This is not to say that SAM is not capable of clearing the latest ultimate.

But it is quite telling that something must be influencing the players' decisions to not play SAM.

For BLM, it is mostly accepted that they are simply a more difficult job to play for prog.
For MCH, their DPS is still undertuned compared to the other phys ranged and offers little utilities of note. Not to mention their damage profile is reliant on GCD-generated resources that suffers a bit from the ultimate fight design.
For RPR, their damage ceiling is comparatively lower than the other melees, and they have a similar GCD resource conundrum as with MCH.

But I definitely couldn't point to what issues SAM could possibly be having right now, not a single thing at all. /s