Там по контексту смотреть надо. Unremarkable, run-in-the-mill, conventional, lackluster, dime-a-dozen, not the sharpest knife in the drawer, и т.д.

Я в комментарии привела контекст. Речь про внешнюю неприметность. Не уверена ,что run-of-the-mill можно использовать в этом контексте (кстати не run in, a run of) ;)
Может Uly подскажет

https://www.multitran.com/m.exe?s=%D0%BD%D0%B8%D1%87%D0%B5%D0%BC+%D0%BD%D0%B5+%D0%BF%D1%80%D0%B8%D0%BC%D0%B5%D1%87%D0%B0%D1%82%D0%B5%D0%BB%D1%8C%D0%BD%D1%8B%D0%B9&l1=2&l2=1

common, plain

MIDDLE-OF-THE-ROAD, common-or-garden

In other words, the cable is relatively run-of-the-mill for a doped fiber optic line.
—IEEE Spectrum, 10 Jan. 2024
Just a few hours before their game against the Cleveland Cavaliers on Sunday, the Spurs posted a run-of-the-mill tweet with game-time details.
—Aaron Valdez, The Enquirer, 7 Jan. 2024
Its product offering doesn’t conform to designs typical of an English shoemaker—don’t expect to find run-of-the-mill brogues.
—Benedict Browne, Robb Report, 2 Jan. 2024
Prisoners working at fast-food restaurants work run-of-the-mill jobs such as fry cooks or others, while those in manufacturing firms sometimes carry out skilled duties such as metal fabrication, welding and precision die casting, according to the class action complaint.
—Aaron Gregg, Washington Post, 12 Dec. 2023

Launched in 1998, the first Bulgari Aluminium proved that run-of-the-mill materials could, indeed, be luxurious.
—Rachel Cormack, Robb Report, 4 Dec. 2023
The attacks happened quietly throughout the city’s busy nightlife, striking run-of-the-mill bars, multistory nightclubs, and underground gay leather bars across two Manhattan neighborhoods, with intoxicated gay men often the targets.
—Matt Lavietes, NBC News, 20 Nov. 2023
That’s day-to-day tipping, though—tips on regular, run-of-the-mill purchases such as cups of coffee, a burrito from a food truck or your monthly trip to the barber.
—Aly J. Yale, wsj.com, 15 Nov. 2023
Not just run-of-the-mill discontent over darker evenings, but the makings of an actual mental illness.
—WIRED, 15 N

ordinary (looking)

not much of a flower (or something else)