> without Apple or the government having power over it
As we are talking about E2EE for cloud storage, governments have very much control over it as in banning the use certain software by law and applying it through ISPs and other means. Not saying I wouldn't prefer a scenario where there was indeed some degree of such choice, but that would not change anything if a government decides it does not want E2EE.
> Apples stance on E2EE is off by default
True E2EE in the context of cloud storage has also certain downsides that one should acknowledge, notably if you lose access to your keys your data is effectively gone. When we talk about a large userbase that includes people who do not have a good understanding of this fact (prob most people) and this choice is not made by themselves in a more conscious manner, this could be a headache for a company (and customer service). Go to subreddits of E2EE encrypted services and notice how often people come up with having forgotten their passwords thus effectively their keys and their data (and that's an audience making a more conscious choice) and not actually understanding that forgetting password + losing any recovery keys = loss of data and that proton cannot give them access back (if they could, there could not be much privacy there). I am not saying that E2EE is bad, but that it is not necessarily the best choice for everybody, and thus I have no issue with apple's opt-in approach.