Basic security for the TP-Link type TD-W9970 Modem Router

[Wurzel]

ADSL modem router TP-Link TD-W9970 refers. It comes with a sheet of paper which gives directions to get started. There is no mention that the default login username and password must be changed for basic security. However, for those that know that this is an essential, the fine print gives a link to the main website to find the user manual. Eventually I find there is only version 2 of the manual with 120 pages. The screens are different so there is a lot of assuming and comparing entailed. All I want is where to change the username and password. Eventually I find it on page 97. Menu item 'System' on the drop down menu. 'System' is there but click away and there is no drop down menu appearing on my screen. The page is blank so I go for html debug. Mess about, change nothing and when the debug screen is closed the drop down menu appears.
Not a word for the novice to realise that they will be flying with no trousers.
I would not know if any other manufacturers are with the same disregard.