Mozilla is unhappy because the use of browser engines other than WebKit will be restricted to the EU, forcing them to develop two different apps.
For an independent browser like Firefox, managing two browsers is not easy, so it can be forgiven that this could be seen as almost harassment.
Also, the fact that the use of browser engines other than WebKit is limited to iOS means that the use of WebKit is still forced on iPadOS, which also increases the effort for Mozilla.
The only way we can regulate any of these big assholes is to start making our own companies. And since there is no separation of big business and government… We need to build big companies ran by the people for the people who can also make policies.
Right now the Gov is for and by the Corperations and not the people… We need to change that ASAP!