I don't think you can generalize like that - Canada (where both the Author and I live) has 4-5 LRT systems, with several more under construction [1]. The light rail in Calgary is the longest, it is not grade separated (it has intersections inside and outside the downtown area). I feel that it also works pretty well. Toronto has the St Clair streetcar and is building the Eglinton LRT, which is/will be partially separated, I also feel they are/will be an integral part of the network. The full separation of Ottawa's system is a big advantage, to be sure, but it is only possible because it is upgrading from a BRT which was also almost fully grade separated (otherwise, land acquisition costs would have been dramatically higher).
The grade separation of the O-train is incidental to the point I was making - an LRT can make a great core of a transit network, using frequent train service instead of route duplication in Bus/BRT service.
They are very popular. The suburbs they service are 20..30km away, and the dedicated roads make the long part of the trip very fast and comfortable. The far ends of the roads looks more like a train station, as they have large car parks surrounding them. Other cities in Australia now look on in envy.
There doesn't seem to be much chance of the buses being abandoned when the budget grows tight. A dedicated 2 lane mostly raised bus highway running parallel to a 8 lane highway isn't much use for anything besides buses, and they weren't cheap to build.
Toronto first built two long subway routes with simple layouts. Suburban residents demanded better transit, so a number of fast, frequent (and therefore convenient) bus routes feeding the subway were created. Fifty years later, ridership on bus routes and subway routes is very high.
Cities that are building LRTs generally have fairly efficient bus systems already. Take Ottawa for a local example - they have had BRT to the suburbs for decades. Fast, separated lanes, etc. They are building an LRT in sort of a mirror of the Toronto system - two central lines, one E-W one N-S, and bus routes will feed into it. The train is fast, frequent, reliable - so transfering will not cause issues. This is being done to replace, essentially, fleets of buses leaving downtown every couple minutes, following the exact same routes for 10+ km before diverging. Replacing that initial section with a higher density mode, and changing the buses into suburban feeders, makes perfect sense.
Aside: I think the title is clickbait, and I think it makes a lot of statements without any citations (eg, "Montreal is much more European in layout and mindset" [so we should ignore it in our analysis]. Or "The area around the LRT lines definitely attract investment, but if you look at who actually uses the line a few years in, itβs mostly rich people.")
Other comment: While it points out Toronto's real bus route successes (high ridership numbers), it ignores the real issues they have had with building more subway/LRT lines over the last 30+ years. They have approved and cancelled some kind of Downtown Relief Line numerous times. Overfull buses is an actual issue in TO.
note: It took me a while to read the article and write this comment, so I'm sure some/all has been duplicated in other comments