Decentralized Security Benefits

It would be too much of a target for hackers.

Eh, it’s herd security. Hackers with credentials may pick off a few people’s accounts, but the odds of you being hit are low since it’s a hard problem to scale and there’s so many targets.

in reality, at some point it's just not cost effective anymore (for the attacker) and other targets become more promising.

Doesn't the action actually prove the point? At the very least, it's proof that the network is vulnerable to this kind of attack. Seeing as it has been ongoing, it can't be that expensive to do, since it isn't really going to result in a financial payoff for the attacker.

Definitely still vulnerable to a targeted attack, but you have fewer attackers than a service provider does by orders of magnitude.

Doesn't it also mean addresses serving as the source of an attack become more disposable?

99.999% of users will never experience a "well-planned targeted attack." Making us jump through the same security hoops that can protect high-value targets is annoying.

Sounds like a bigger attack surface for malicious actors.

The hole point about this sort of things is you can detect mass attack. If only one person finds a problem all get the benefits.Its much harder to make a targeted attack, specially if you are not google or have the full support of google.Nothing is perfect, but there is very little that is better.Your other options are only not using the devices at all.

It's the difference between finding an expliot for gmail vs finding one for a small discord server. Your attack on gmail has a bigger universe of targets if successful.