This is fundamentally not how Signal works, but you are generally correct in that a phone number has been shown to provide a lot of context for a person (or a device, at least). But Signal (the app) only uses a phone number for initial verification of an account. You have a lot of options to break that association with you - use a landline and get a call verification code, use a VoIP number (assuming you trust the provider), use a burner SIM, etc.
Once you have an account, you can choose to identify yourself on the network solely via username so the registration number is not presented to other users. The Signal protocol itself is well-audited and generally secure.
If your issue is with Signal the American company, use an open source fork like Molly with your own UnifiedPush instance. Then you’re only trusting them with transport of your encrypted messages, which again have shown to be secure at least in public audits.
Hey now, the US has its own low-cost drone reverse engineered from an Iranian one-way attack drone.
Does that mean they’ll stop building Tomahawks? Of course not, now two companies can benefit instead of one. That’s 2x the military-industrial complex baby!