The answer is certificate pinning. For example, it is impossible to MITM google services if you are using Chrome because the correct public keys are hardcoded in the browser itself.
If the site certificate is not pinned, you can use a 3rd party service hosted outside the MITM proxy to compare certificate fingerprints (such as https://www.grc.com/fingerprints.htm)
If the site certificate is not pinned, you can use a 3rd party service hosted outside the MITM proxy to compare certificate fingerprints (such as https://www.grc.com/fingerprints.htm)