It is not straightforward, and it is complicated by a number of factors. The first would be bad "brand hygiene": If a company has dozens of legitimate domains across different TLDs, different providers and different geographical locations then it's already more complicated than just one canonical .com domain. If teams within the company are permitted to spin up their own domains (e.g. marketing campaigns, branch offices) then it gets 10x worse. Lastly if a legitimate brand frequently changes its appearance, it will be harder to pin down the true brand identity.

But even if you follow all of these best practices there are still powerful attack vectors. A threat actor could host their phishing page on an unrelated (compromised) domain with good domain reputation, in that case you wouldn't even know about that site until the first email or SMS hits your customers. Or the threat actor could use one of the many file-hosting or website services to create their site and host it on a shared third-party domain with perfect domain reputation (e.g. amazonaws.com).

And then there's incentive: It's no the companies that suffer financial losses, it is their customers. If you were talking about their employees being phished that would be a different story. Same thing for Google Safe Browsing: Their incentive is to protect against most of the obvious phishing, without any false positives, ever. If they are slow to detect something they won't suffer any losses. If they generate a False Positive their Chrome browser might suffer significant reputational damage if a popular legitimate domain is blocked.