So what happened? Why aren't we in a world of abundant energy?

It's because safety wasn't the obstacle to nuclear energy, cost was.

Also, I don't think passive safety of CANDU is what's meant by passive safety of HTGRs. The latter can survive losing cooling and everyone just walking away (in theory); I suspect the CANDU melts down in that situation, even if the chain reaction does stop.

If you use these reactors, you have no other reason to produce weapons grade uranium. That's the only thing that sticks out to me.

Dealing with nuclear waste is still a thing, even with safe reactors. Here in the US, we can't seem to find a permanent place to bury waste.

Don't forget, either: Nuclear waste isn't just spent fuel. The reactor core remains radioactive after the plant is decommissioned.

That's one of the things that nuclear fusion proponents seem to forget. Even without the spent fuel problem, fusion reactors still produce nuclear waste.

Turns out a steam based thermodynamic cycle is expensive even with "free" energy.

Current price of Nuclear in Ontario (generated by CANDU reactors) is 5.9 cents per kWh.

That is very expensive. Given that they came online in the 70s and early 80s we can assume the initial capital investment is paid off by now and that cost is only the marginal running cost. (OPEX)

Now, currently we are building solar farms in desert areas for ~1.5 cent per kWh. Including both CAPEX and OPEX. On-shore wind is built at ~3 cents per kWh and ~6 cents per kWh for off-shore.

This is where the explosion of renewables is coming from, they currently undercut the marginal cost of traditional power sources.

Sorry, that's what the consumer pays. It includes transmission to the home.

That does not appear to be correct.

https://www.oeb.ca/consumer-information-and-protection/elect...

Now tell us what happened the last time they tried to buy more nuclear plants.

Simple answer; Infinite greed and lust for (political) power…