The only real alternative to checking who signed a certificate is checking the certificate's fingerprint hash instead. With self-signed certificates, this is the only option. However, nobody does this. When presented with an unknown certificate, people will just blindly trust it. So self-signed certificates at scale are very susceptible to MITM. And again, you're not going to know it happened.
Encryption without authentication prevents passive snooping but not active and/or targeted attacks. And the target may not be you, it may be the other side. You specifically might not be worth someone's time, but your bank and all of its other customers too, probably is.
OCSP failed. CRLs are not always being checked. Shorter expiry largely makes up for the lack of proper revocation. But expiration must consequently be treated as no less severe than revocation.