angela Signal / Molly would be better without a phone number, you can buy a virtual phone number in cryptocurrency (preferably Monero) and try with it, but I don't think it's a big concern for most users, that Signal is only good for extremely low threat models is a very exaggerated claim, it's still good, the phone number is encrypted and not stored, you can also hide it from your contacts.
A phone number is not proof and if someone reports you, it's not the technology's fault, it could happen whatever messaging you use, but I agree that SimpleX probably does things better. If your threat model is very high, you should think about a good OPSEC first.