Pre-set routes seem distinctly worse. By definition they don't flex to handle new / temporary traffic patterns. Though they do have a super-huge benefit of not needing an app / real-time requests - in some cases that's a requirement.
Americans own cars because it's convenient to do many different things with them. If I own a car and my child is sick, I can go get medicine from the all-night pharmacy. I don't want to give up that power just because social planners think I should be happy with a bus or car that I have to plan my life around, not the other way.
This obviously holds less true the further from the city you go but what I'm trying to get at is that you can own a car and still benefit from good public (or in this case, alternate) transport. I still need to keep the car registered and in working order to transport my double bass from time to time and want to keep it that way for all the benefits that you described. What I don't is for me to be shackled to the thing as my only form of transport, much like you don't want to be shackled to a bus timetable.
Just because these services exist, doesn't mean that you need to give up your car to benefit from them (and that's not even going in to benefits provided to people in your community who CAN'T drive).
The not so fun part of it is that if the minivan you are in has nine seats and there are already, say, twenty passengers on it, plus a couple of chickens, the driver will still stop by and collect additional passengers! :)
Minus the chickens of course..
Like buses, you just wait for the next one. So yes, it's a trade-off. Doesn't replace taxis. But it's damn nice when buses aren't readily available, and way more friendly.
The two main issues they encounter, which are related to being private and decentralized, are that routes collect around a few hubs(e.g. "downtown" or "hospital") that guarantee customers, but get vastly over-serviced without a corresponding cross-town option; and they don't have a dedicated right of way, and end up fighting through the city traffic, sometimes getting stalled for hours by uncontrolled, massively over capacity streets.
There is a lot of room for technology to improve on this - if the governments got into the picture and ran a minibus app, they could track and subsidize those services to formalize it, encourage use and reduce inefficiencies, allowing a transit grid to be formed with little formal capital.
But maybe, yeah..
I saw a lady walking along the side of a rural road - this was about 12 years ago, so there weren't buses then, and there won't be in the next 12 years either - so I pulled over and asked her where she was going. Turns out she was going to walk, in the summer heat, to a grocery store about 10 miles away.
We shared my car just fine. But I certainly wouldn't go over to a neighbor and ask for a ride to the grocery store if my car was running ok.
Edit- also, they are still not regulated well as I know of someone who was driving one and he does not even have a drivers license.
In rural communities here in Chile, and also in smaller towns, there is an amazing solution to this called Collectivo. I had never heard of it before arriving, but man it's the greatest thing. It's something in-between a bus and a taxi: a taxi with a predefined route. So if you're on a route, which there are many, you flag down a collectivo as it passes, and since both you and the driver already know where it's going, it'll stop for you even if there are already people in the car.
What makes this amazing is that it's cheap because the route is pre-set, and it's shared, and the driver can just go all day knowing there will be people along the route, and doesn't have to finish one ride before starting another. But meanwhile they'll generally go partially off their route if you request it, and it's not too much of a bother.
Why don't North American rural areas do this? It's a really great way to get around, and makes it so you can live (or at least visit) in rural areas without owning a car.