Uber Shuttle works in my home city since 2019. It's Kyiv, 3mil population, ancient public transportation network but probably a bit better than USA (by hearsay).

While it was working in normal conditions (before Covid and war) it wasn't that good. Routes were limited and timing iffy. Inside it was a regular small bus, so nothing fancy. And more expensive that public transport. So it is a serviceable transportation if there are no normal bus available at your route and at the same time uber shuttle route is matching yours. But any proper city transport beats them on all counts.

PS: from the article it seems this is not about Uber Shuttle feature, but a different new ride share feature. Anyway, I'll leave my comment, but consider that it is not quite relevant.