The monorails were slow, inefficient people carriers and all required
stairs to get up to them and have low passenger counts.
They needed support structures along the streets which were in the way of everything.

Thanks Bazz
Despite being 'a sardine' , we travelled on monorail in Kuala Lumpur, pre covid of course. We often had to wait for next one, so realise old types not ideal for busy commuters due to limited passengers and only a few carriages.

The monorails were slow, inefficient people carriers and all required
stairs
RunninRib,

Any of you ever heard of technological advancement ? Aeroplanes used to be slow & required stairs !
Cars used to be inefficient, all things of the past were improved. Mono Rail can not be ??
It appears the only thing that can not be improved is the mentality of some people !
How about thinking future investment rather than instant profit ?

Indi; have you ever been on a monorail ?
There are other techniques such as the magnetic lift systems but they
are not monorail but some I have seen videos of are elevated.
As far as I can see, the only advantage monorails possess are very sharp curves.

individual: The construction of monorail lines is more expensive than surface trains. To build a surface train line*, for most of its length, you just have to push dirt around then lay track, but for a suspended monorail line the whole thing is a complex engineered construction. However, one area where monorails do have a advantage is that if they are built over existing public land (such as roads/foothpaths or waterways) you don't need to buy the land. An underground train shares this advantage of monorail (ie: often you don't have to pay for the ground it runs through).

Regarding the cost of monorail rolling stock (ie, the monorail carriages), they are more expensive than trains because trains are a well developed technology. Many companies around the world can produce trains and many parts (such as bogies/suspension & wheelset, brakes, couplings, etc..) are commonly produced to standard specifications, but monorail vehicles on the other hand are completely bespoke and require uniquely specialized ground-up design.

[* I'm talking about surface trains that run along the ground here, there do exist quite a few completely/or/mostly elevated train lines around the world: lines with two tracks and not monorail]

There is a major divide in rail transport.
Commuter and intercity.
There is also another divide passenger and freight.
I have seen statements that Very High Speed (VHS) passenger cannot be
mixed on the same track as freight.
That appears to be one reason VHS is uneconomic in Australia.
However Fast Enough passenger and freight are mixed on the same track.
Fast Enough about 200km/hr on straightened, regraded and built to
higher standards would enable a six hour Sydney to Melbourne and
similar times to Brisbane.
Those times are city to city not home to home.
Likewise you must compare with home to airport, wait time, airport
to airport, to home and air will still be quicker but not by that much.
However either because of the greenies, or as I believe because of
the oil companies, air travel will not be an option, either for
political or economic reasons.

Outside of this argument one of the reasons the VFT proposal Sydney
Brisbane failed was the land form north of Sydney, it required a
high level bridge across the Hawkebury river and tunnels that
would cost more that the Sydney Harbour Bridge would cost today.
Also the tunneling required to enter Sydney would add a lot of time
to the trip time from both north and south.
I believe the 2nd airport at Badgeries Creek could be converted into
a VFT rail terminal.