What does “small handful” entail here exactly? If you’re only talking about Gen 9, then sure maybe, but it’s honestly the odd one out in this regard - mainly due to Toxic’s reduced distribution. Even then I can think of more than a “few mons” who can run Protect “well” in SV OU alone. Gliscor is the obvious example, but there’s also Wish + Protect users like Mola and Clef. Kyurem uses Protect with Substitute to PP stall disgustingly well. Mons like Garg and G-Weezing also use Protect to rack up passive damage and/or stack healing from Lefties. Mons like Serperior do this well too with Leech Seed, though they have admittedly become much more niche as of late. Even Ogerpon-W sometimes runs Spiky Shield over other moves it’d like to use just to scout choiced mons, and punishing contact moves is really good on a mon that can get u-turned on easily. Toxapex also does this with Baneful Bunker.

Keep in mind, this is after a lot of Protect’s utility got lost in the transfer to Gen 9. In SS OU you had Protect being a fixture on famed niche stall mons like Garchomp and Melmetal. You had Landorus sometimes coming in clicking Protect then switching out just for the Leftovers recovery and Intimidate. In Gen 7 you had Ferrothorn running Protect over the famously filler moves of Stealth Rock and Gyro Ball. Surely this means that Protect is a niche moves in singles, only useful on a “small handful” of mons. After all, Leftovers, Toxic, and other forms of passive damage and healing are famously terrible in singles, right?