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.
You cannot root out the evil from within such massive companies. Nvidia still has a stranglehold on the market with CUDA. Literally the only thing one can do is to employ their wallet towards more fruitful endeavours, like donating and purchasing Android in this case. People who are invested into Apple are going to have to face that they made a choice moving away from freedom, even though I understand that staying the odd one out socially isn’t a lot of fun. There’s nothing to be done here unless someone with a lot of money and lawyers sues Apple. Know anyone willing to do that?