haveibeenpwned.com has been offering the same service for free for years.
haveibeenpwned will notify you if your email address was in a breach.
The Mozilla offering seems to include the same, but also cover other pieces of personal data, and the ability to request removal from data brokers.
And yes, you could probably go and ask the brokers directly, but that is certainly a lot of time and effort, so paying for it might make sense, assuming you trust the service provider.
The new thing is scanning for your info at data brokers (for free, but USA-only), and automatically removing them and continuously checking that they stay removed (paid, US only).