Vegas has never had meaningful public transit investment, and a real subway would cost billions and take decades of political will that simply doesn’t exist here. The Loop fits the actual use case: moving convention attendees between LVCC halls and eventually casino properties, quickly, in a city where distances are deceptive and walking in 115° heat is brutal.
For that narrow purpose, point-to-point, climate-controlled, short-hop movement in a dense tourist corridor, it works reasonably well. The comparison to a subway is a bit of a category error; no subway was ever on the table. The real question is whether it beats surface-level shuttles and moving walkways, which it probably does.
The critique is fair though: it’s not scalable the way a subway is (throughput is limited by number of cars), and it’s privately owned infrastructure serving commercial interests rather than a public transit network.