The technologies used in Signal protect a lot against metadata leakage. Group information is encrypted, your contact list isn't stored on their servers (it is sent but obscured and uses a lot of tricks to make it harder for them to access it). They also have sealed sender which enables them to reduce the metadata they collect.

And he is right to point out that that immediately invalidates most of the privacy benefits due to metadata leakage.

That's just not true? Switching from Messenger to Signal will always be a huge step up regarding privacy and security, no matter what your threat model is. Some metadata potentially (we don't have any evidence that Signal has ever leaked anything) leaking is much better than knowing your metadata (and data) is being used to track you constantly...

I think you are not the target of this video. The target of this video are people who do not think about threat modeling at all and just assume it is safe to use because e2ee and Signal marketing BS and continue using these services the exact same way as they used gmail or Facebook messenger before

What? If someone doesn't think about threat modeling I either explain it to them or build a reasonable model for them. I don't tell them to go live in the woods because otherwise there is one bit of information about them that might leak...