If you want to advertise, have a newsletter that people can opt into.
If you need money, allow people to pay for just Firefox.
Everyone gets angry and has an opinion of how this sucks. There's no way for this to work out for Mozilla. Nothing they do will work or make everyone happy.
Google won.
It's fine for them to create Mozilla VPN. It's never, ever fine to use the same old dark bullshit patterns, and interrupt me on all my computers, same as all these other dirtbag tech companies. They are supposed to be different, and give a shit about the user. Sorry if this is their only way to advertise, but it's not okay.