Personally, when I've cycled in London, I haven't found small private passenger vehicles (be they owned, hired via an app or hired via sticking your hand out and paying cash) to be a massive threat. It's large, mostly commercial vehicles (building and delivery lorries and White Van Man) that cause the main issues for cyclists, both in terms of actual risk and in terms of making it feel oppressive.
(Taxis are no more space or pollution efficient than private cars, so I see no sense in considering them any differently)
Absolutely - commercial vehicles (especially large ones) are a big danger to cyclists too. But I was commenting specifically on the suggestion that there were very few "cars" on the road in the daytime in central London, and pointing out that on my patch that's certainly not the case. That's why my comments were focussed on cars and car-like vehicles. I wasn't meaning to ignore the problem of commercial vehicles.
In terms of danger though, "minicabs" do seem to be in a class of their own these days. Their dangerous and illegal actions have caused me far more problems in the last few years than I was used to from similar smaller vehicles. Like most cyclists in London, I've had run-ins with buses and taxis over the years, but nothing like the problems I have now with the increased numbers of minicabs/Ubers etc.
Incidentally, as far as "proper" taxis are concerned, I do see them as part of the public transport system, and as a useful emergency back up to buses etc, and as needed for people with mobility problems. Providing they continue to switch to electric vehicles, and continue to be wheelchair accessible, I see them as part of the solution [to the need for safe, healthy, equitable urban mobility], not as part of the problem.