But you only really need one to say it’s authentic. There are levels of validation that require different levels of effort. Domain Validation (DV) is the most simple and requires that you prove you own the domain, which means making a special domain record for them to validate (usually a long string that they provide over their HTTPS site), or by sending an email to the registered domain owner from their WHOIS record. Organization Validation (OV) and extended verification (EV) are the higher tiers, and usually require proof of business ownership and an in-person interview, respectively.
Now, if you want to know if the site was compromised or malicious, that’s a different problem entirely. Certificates do not and cannot serve that function, and it’s wrong to place that role on CAs. That is a security and threat mitigation problem and is better solved by client-based applications, web filtering services, and next-gen firewalls, that use their own reputation databases for that.
A CA is not expected to prevent me from hosting rootkits. Doesn’t matter if my domain is rootkits-are.us or totallylegitandsafe.net. It’s their job to make sure I own those domains. Nothing more. For a DV cert at least.
Public key cryptography, and certificates in particular, are an amazing system. They don’t need to be scrapped because there’s a ton of misunderstanding as to its role and responsibilities.