The good:
Twitter should not be editorally curating people through verification, making verification only about ID and being a real person is a broadly good change, as long as it's not necessary for participation. Brands, celebrities, those in the public eye could benefit from this. Needs to be implemented with care and ideally with a branding change so as not to confuse users as the semantics change.
The bad:
$8 is way more than the profitability of an ad supported user. There's no excuse for "half the ads", it should be none at all. See: every streaming service. (Edit: ok some streaming services have ads, but for most online content - video, journalism, etc, if you subscribe there are no ads, it's just nickle-and-diming users to give them a bunch of ads, particularly when the marginal cost for Twitter Blue is essentially zero).
The ugly:
Paying $8 to get your voice heard by more people biases towards those with means rather than those contributing to the conversation. At best this will reduce conversation quality on Twitter, at worst this is ripe for abuse.