RSA signatures aren't really an issue. Big, but not that easy to screw up. The (biggest IMO) problem with RSA is that unlike ECDSA or ECDH or EdDSA it's usable

RSA signatures aren't really an issue. Big, but not that easy to screw up. The (biggest IMO) problem with RSA is that unlike ECDSA or ECDH or EdDSA it's usable for BOTH signing AND encryption, and re-using the same keys for both signing and encryption can be catastrophic (if you screw up the padding, which is another uniquely-RSA footgun). It's far, far easier to have a signing algorithm with signing keys, and an encryption algorithm with encryption keys than it is to have a single algorithm that does everything but requires the user to get all the options right. By working the same "both ways" RSA makes asymmetric key management even harder, and it's already one of the hardest parts of cryptography!