>> Yes, your are right. That is the weakness. That is the reason why it his highly advised to look at your supported cipher suites on the client side and disable the weak ones.

You absolutely should configure all endpoints only to use adequate cipher suites, but that's simply because the bad ones shouldn't be used and as a client you don't want to rely on the server being well configured (and vice-versa).

HOWEVER - that does not mean a handshake MITM is possible, the protocol accounts for this, please see my parallel reply to yours.