Yes. For me reasons of VPN on Android (even with Google) are following:

1. Most of greedy apps are trying to collect info about your location. Because in most of the cases you will restrict direct access to the location data, apps will try to do it through IP. VPN resolve this problem at all.
2. A lot of greedy apps or websites are trying to do fingerprinting to identity your logs. While it is possible in theory to do fingerprinting by fuzzy matching all-logs against all-logs, the task is so computationally heavy that the only way is to try to do fuzzy-matching (aka fingerprinting) within the locations. VPN allows you to hide your location.

Of course one may say that VPN does not provide a 100% protections from fingerprinting, I think there should be applied the same approach like in cyber security: the goal is not to protect yourself by 100% but to make attack so expensive that it does not make sense. VPN makes fingerprinting so hard that noone will really do it until you are a journalist, intelligence officer or something like this.

For me it’s pretty much mandatory because Youtube is normally blocked :/

I use another app to watch youtube, not their official app or official website.

It depends who you are trying to hide from. A VPN will hide your internet traffic from your ISP/phone company, but obviously not from the site you are visiting.

At best you might be one of may people connecting from the same (VPN) IP address, but they can still collect info from your browser/app etc to generate points to ID you if they want.

Is this even possible? My impression is that nowadays Google, whenever they have the impression that a connection to YouTube may been proxied, require a sign-in to prove that "“you are no bot” (I wonder which bots are watching YT videos), but in fact to avoid access via VPN or proxying via Invidious or Piped.

That’s the reason why YouTube is essentially dead for me now.

Online privacy typically requires that you think of what you are trying to protect yourself from.

So, what are you trying to prevent?

A VPN will make your public IP address private. This can hide some activity from your ISP, hackers, marketing companies. However, it’s only one layer of protection.

(You could also use NewPipe as a replacement to the YouTube app.)

However, some VPN companies will track you and sell your information. Because of this, I recommend ProtonVPN (free tier, Swiss-based, encrypted traffic that they can’t even de-anonymize).

If you want more complete privacy, you’d want to use something like a Tor Box, but these aren’t typically good for streaming because the layered routing makes for a slow Internet connection.

A VPN does not provide inherent security. It is only as trustworthy as the entity providing it. As I understand it, A VPN to a safe LAN with firewall or such, yes. A VPN to a sketchy third party that will basically log everything you do, no.

Hide your traffic from isp. Actually android can be independent from google in various ways like grapheneOS installation. As you said there is no point in using vpn in a phone that bundled everything google. But if you did the things to protect your privacy like switching to privacy focused services (youtube app to newpipe) then vpn worth it. Anyway vpn alone not a full proof.

InviZible Pro is a good option. Download from F-Droid

You can use firefox. Or degoogled andoid rom. Google spies on your phone mostly through their apps: chrome, maps…

Andoid by itself is very privacy focused operating system.

Check c/degoogle on how to remove google stuff from your phone. Also check privacy guides about vpns: https://www.privacyguides.org/en/vpn/

They are mostly not what they are advertised as. You should check tor. And maybe /e/os