Would I prefer government enforce building safety codes, or let consumers decide what they want?
Would I completely ignore the fact that Google has sucked the air out of the room with their market dominance, so hardly any competitors are left for consumers to decide between?
We can all easily name multiple email and subscription music providers.
The third case is not actually a singular case. When we are talking about consumer facing services, there are many competitors in most cases. I suspect that it would even be difficult to make anti-trust arguments since the factors that funnel people towards Google is largely outside of Google's control.
Google's behaviour towards businesses is a different matter. While businesses may turn to the competition, their dominance means that avoiding Google will have negative consequences.
Sure your business is destroyed, but you're right, you can easily get a new email address.
The WhatsApp founder seems pretty against Facebook and is encouraging and funding Signal. He took money from a company he doesn't believe in or like because who wouldn't. And this is despite him not liking Facebook. So realistically competition is great on paper, but in this case the competition already has such market dominance that any new company that tries will get squashed with a buy-out or other aggressive tactics. So realistically I don't see how competition will do anything.
And when so many businesses are at the mercy of a few giant companies, we probably shouldn't deny them protection with the "it's a b2b matter" dismissal.