Hence why I said 'this particular line OF COMMENTS' and not 'this thread'.
Security and privacy are not the same thing, nor are they directly related. Lack of privacy can literally be designed into a secure system, which is one way of describing how Chrome works. It doesn't really matter how you choose to esoterically define the words if everybody else's meaning is different.
When people talk about Chrome being secure, they're talking about the browser's resistance to being compromised by a third party. It's that simple. Nobody cares that you have some esoteric view whereby Google's inherent lack of privacy protections, wherein Google is able to collect information about the user through their browsing habits, is also part of the browser. That is a matter of privacy, not security, and Google very clearly sets out all the ways it collects information about the user in its various policies. Security relates to whether third parties - using the browser architecture itself as a conduit - are able to compromise the browser in such a way as to obtain or manipulate user information, data, or elements of how the user interacts with the system, in a way that is not approved by the user and about which he is likely unaware. Every user of Chrome agrees to Google's collection and use of certain data, and ergo such data collection does not involve security issues whatsoever. That you might disagree with Google's privacy policies is not to the point. Note that if the aggregated user data were to be surreptitiously accessed by a third party, this WOULD be a security issue - but that isn't what we're talking about, is it?
If talking about security, Chromium has been the most secure browser for at least a decade. Safari and Firefox are significantly worse at security than Chromium browsers are. That's not really debatable - just go look at results of the various hacking contests, look at the number of active exploits and how long they are in the wild and unpatched, etc.
On privacy, Firefox is undoubtedly better, although Mozilla has had snafus over the years. Mozilla also literally makes something like 99% of its revenues through agreements it has with Google search, so go figure.
One final note - as has been the case for at least 15 years now, Firefox with uBlock Origin and NoScript and a few other addons are probably the most secure you can get, albeit at significant cost to usability and convenience. When discussing security I think it's inherent that people are discussing the vanilla, out of the box install of a browser. Having said that, I currently use Brave and find it to be the best mix of features of Chrome without the rest of the Google privacy problems; despite being a very long time Firefox user, it just isn't good enough these days, although if Google succeeds in killing adblockers in Chrome I'll have to move to Firefox regardless.
Good day.