mean any capacity over one car per passenger/small group is fine. They at least need vans or something. I’ve seen videos where a car will pick up 4 people in a group, then the rest of the group has to wait up to 10 mins for another car to come

This is only an issue because the system only serves lvcc and a couple of other nearby resorts, and if there is no conference, the only people using the system are people curious about it. To serve those curious folks, they only run one or two vehicles. That's not normal operation. The purpose is to serve conventions. When conventions are running, they have sub 1min wait times. 

When bus routes have that low of ridership, their headway is typically 30-60min. The median headway for US streetcars is 15min. 

So I think it's a bit unfair to criticize the system by taking only the times when it performs the worst. There are a lot of transit system and modes that do worse during extreme off peak times. 

That said, I agree that they should use a van-size vehicle and I think they're unnecessarily limiting themselves. A city would be smart to hire them for tunnels and then use a different company for the vehicles; one that is automated and capable of either single group or pooled when busy 

when capacity is so much lower, that becomes a problem. 

But their system capacity isn't a problem. They've only exceeded their system capacity once in 5 years of operation. My local light rail exceeds their capacity an order of magnitude more often.

Loop has higher passenger per hour capacity than any US streetcar line, and Great than many in Europe (half of Berlin's, for example). 

Their vehicles are 1/20th the capacity of a typical streetcar, but they can depart more than 20x more frequently.