Oracle 19c

Regular users are not allowed to login "as SYSDBA" unless user has been granted this role. To the right in your screenshot you have selected the role "SYSDBA". If you rather select the role "default", you will be able to login.

All the different roles in the drop down list are roles you can grant to users. These roles have specific administrative purpose.

When role granted and selected in SQL Developer at login, this user will be granted administrative privileges to handle everything regular users are not going to worry about like startup, shutdown, backup, storage-management

Why so complicated?

In a huge corporate-bank you will most likely separate the guys who do backup from the guys who do storage-admin from the guys who do dba work. In your world where you have everything installed on your laptop, all this seems like complicated things. Remember you have installed enterprise software on your machine and these security constructs are means to restrict administrative access.

The most common connection construct you will see when doing administrative work on your Oracle Database engine is this

sqlplus sys/password@<TNS_ALIAS> as sysdba (via SQL net) or sqlplus / as sysdba (OS auth)

Best of luck!