Realistically none of these are very good options. Starting a competitive messenger application is likely to be impossible - Signal got to where it is thanks in large part to 50mn USD from Whatsapp's founder. The fact that it's very difficult means that there aren't a huge number of competitive choices, and none that are "Signal but you can access your data". So even though complaining is not a great option, it might be the most likely way to get what is wanted, whether by someone from Signal seeing the request and agreeing, or someone else seeing there is a market for this.
If you have a choice between Whatsapp (metadata not private, but has backup) versus Signal (metadata private but no backup), if you need backup (or anyone you communicate with does), you lose privacy because you're forced to use Whatsapp. Arguably because of Signal's refusal to "compromise" on privacy by allowing backups you have lost privacy anyway.