It is still quite common that credentials are transmitted in plain text over a secure communication channel (HTTPS). In case the communication channel is not encrypted we are talking about an entire different problem.
The key here is that the communication channel is encrypted with strong cipher suits. When performing a man in the middle attack (e.g. sniffing the connection), a certificate error is displayed on the client's browser.
Is it important to encrypt the password send by login forums of websites and if yes how badly it can affect?
From my personal (attacker) perspective it doesn't really matter whether you transmit the plain text password or an encrypted or hashed version of the original password.
Once either one is obtained through a man in the middle attack, they can be replayed / re-used by an attacker.
However, one significant difference is that the server will never receive the plain text password when the second option in the diagram is used. Therefor it will not reside in memory.
In case TLS is stripped from a load balancer and requests are transmitted internally over HTTP this would be considered a better approach.
As you can see, it depends on what you consider a threat and what you are defending against.
Please note that a TLS should not be considered the "holy grail" and that defense in depth should be applied when ever possible.